1 00:00:05,101 --> 00:00:07,370 NASA's JET PROPULSION LABORATORY 2 00:00:07,370 --> 00:00:10,040 PRESENTS THE VON KARMAN LECTURES. 3 00:00:10,040 --> 00:00:12,909 A SERIES OF TALKS BY SCIENTISTS AND ENGINEERS WHO ARE 4 00:00:12,909 --> 00:00:16,196 EXPLORING OUR PLANET, OUR SOLAR SYSTEM, 5 00:00:16,196 --> 00:00:33,079 AND ALL THAT LIES BEYOND. 6 00:00:33,079 --> 00:00:40,470 GOOD EVENING, LADIES AND GENTLEMEN. 7 00:00:40,470 --> 00:00:42,222 HOW IS EVERYONE TONIGHT? 8 00:00:42,222 --> 00:00:43,540 THANK YOU FOR COMING OUT TO JOIN US. 9 00:00:43,540 --> 00:00:47,494 ATOMIC CLOCKS ARE ALMOST INVISIBLE TO MODERN LIFE. 10 00:00:47,494 --> 00:00:52,115 FOR EXAMPLE, THEY PROVIDE THE FOUNDATION OF THE GLOBAL 11 00:00:52,115 --> 00:00:55,185 POSITIONING SYSTEM ENABLING AN ENTIRE INDUSTRY OF LOCATION 12 00:00:55,185 --> 00:00:58,355 AWARE APPLICATIONS, AND THEY UNDERPIN THE GLOBAL FINANCIAL 13 00:00:58,355 --> 00:01:05,161 AND TRADING SYSTEM WHERE TRANSACTIONS HAVE TO BE TAGGED 14 00:01:05,161 --> 00:01:06,012 TO MILLISECOND PER SUGGESTION. 15 00:01:06,012 --> 00:01:10,066 THEY HAVE BEEN THE FREQUENT STANDARD FOR THE DEEP SPACE 16 00:01:10,066 --> 00:01:20,060 NETWORK WHICH TRACKS THE MULTITUDE OF THE SPACECRAF 17 00:01:20,060 --> 00:01:21,478 DEMONSTRATION MISSION HAS BEEN MATURING THE LATEST TECHNOLOGIES 18 00:01:21,478 --> 00:01:25,165 INTO A SMALLER, LESS MASSIVE PACKAGE SUITABLE FOR 19 00:01:25,165 --> 00:01:31,388 INSTALLATION ON A VARIETY OF DEEP SPACE PROBES TO ENHANCE 20 00:01:31,388 --> 00:01:34,241 NAVIGATION PRECISION ACROSS THE SOLAR SYSTEM. 21 00:01:34,241 --> 00:01:39,479 WE'RE LUCKY TO HAVE TWO GUESTS TELL US. 22 00:01:39,479 --> 00:01:48,121 DR. TODD ELLIE IS A GRADUATE OF PERDUE UNIVERSITY AND FORMER AIR 23 00:01:48,121 --> 00:01:51,057 FORCE OFFICER. 24 00:01:51,057 --> 00:01:55,495 HE'S BEEN AT THE JET PROPULSION LABORATORY SINCE 1999 DEVELOPING 25 00:01:55,495 --> 00:01:59,165 NAVIGATION SYSTEMS AND ARCHITECTURES FOR MANY PROJECTS 26 00:01:59,165 --> 00:02:05,288 BE AND SMALL INCLUDING THE MARS NETWORK, FORMER CONSTELLATION 27 00:02:05,288 --> 00:02:18,201 PROGRAM, AND LUNAR LANDER. 28 00:02:18,201 --> 00:02:22,272 DR. FORRINGTON IS A GRADUATE OF CAL TECH. 29 00:02:22,272 --> 00:02:25,191 HE HAS DEGREES IN ELECT CALL ENGINEERING AND MORE THAN 25 30 00:02:25,191 --> 00:02:29,362 YEARS OF EXPERIENCE IN HARDWARE AND SOFTWARE DEVELOPMENT. 31 00:02:29,362 --> 00:02:33,466 ALMOST 20% IN SPACE APPLICATIONS. 32 00:02:33,466 --> 00:02:36,519 PLANETARY SCIENCE, AND SPACECRAFT TECHNOLOGY 33 00:02:36,519 --> 00:02:37,237 DEVELOPMENT. 34 00:02:37,237 --> 00:02:42,042 OTHER THAN SPACE THAT RIGHT, ALAN'S INTERESTS TEND TOWARD 35 00:02:42,042 --> 00:02:44,477 COLLEGE HOOPS AND BALLROOM DANCING. 36 00:02:44,477 --> 00:02:49,215 LADIES AND GENTLEMEN, PLEASE HELP ME WELCOME TONIGHT'S GUESTS 37 00:02:49,215 --> 00:02:55,305 DR. TODD ELY AND ALAN FAIRINGTON. 38 00:02:55,305 --> 00:02:56,323 [ APPLAUSE ] >> THANK YOU, MARK. 39 00:02:56,323 --> 00:02:58,241 THANK YOU FOR COMING. 40 00:02:58,241 --> 00:03:04,264 ALAN AND I EXCITED TO TALK ABOUT THE ATOMIC CLOCK PROJECT TODAY. 41 00:03:04,264 --> 00:03:07,167 THE DEEP SPACE ATOMIC CLOCK PROJECT IS DEVELOPING AN 42 00:03:07,167 --> 00:03:14,057 ADVANCED PROTOTYPE OF A NEW TYPE OF ATOMIC CLOCK THAT WE HOPE TO 43 00:03:14,057 --> 00:03:16,076 DEMONSTRATE IN LOWER ORBIT IN THE NEAR FUTURE. 44 00:03:16,076 --> 00:03:22,132 NOW THE ATOMIC CLOCK, OBVIOUSLY, CAN TELL TIME VERY ACCURATELY. 45 00:03:22,132 --> 00:03:26,052 BUT THAT'S NOT HOW WE'RE INTENDING TO USE IT FOR. 46 00:03:26,052 --> 00:03:26,486 NAVIGATION AND SCIENCE. 47 00:03:26,486 --> 00:03:31,341 IT'S A KEY COMPONENT TO THE ASPECTS, AND SO OVER THE COURSE 48 00:03:31,341 --> 00:03:35,178 OF THE NEXT HOUR OR SO, WE WOULD LIKE TO TALK ABOUT HOW CLOCKS 49 00:03:35,178 --> 00:03:41,067 AND TIME PLAY A ROLE TO THE SCIENCE WE DO IN DEEP SPACE, AND 50 00:03:41,067 --> 00:03:49,459 TO BEGIN THAT WE HAVE A VIDEO TO SET THE STAGE. 51 00:03:49,459 --> 00:03:56,399 >> TIME SEEMS TO RULE EVERYTHING WE DO. 52 00:03:56,399 --> 00:03:58,268 IT'S IMPORTANT TO US. 53 00:03:58,268 --> 00:04:05,992 THE HOURS AND MINUTES OF OUR DAY IS -- 54 00:04:05,992 --> 00:04:10,380 ♪ ♪ OFTEN OVERLOOKED IT'S A CRUCIAL 55 00:04:10,380 --> 00:04:15,268 PART IN ANOTHER AREA OF HUMAN PROGRESS. 56 00:04:15,268 --> 00:04:16,086 NAVIGATION. 57 00:04:16,086 --> 00:04:19,139 WHAT DOES TIME HAVE TO DO WITH NAVIGATION, YOU ASK? 58 00:04:19,139 --> 00:04:26,413 WELL, GOT A SECOND TO FIND OUT? 59 00:04:26,413 --> 00:04:30,050 SEA EXPLORERS CARRIED CLOCKS ON TOP THEIR SHIPS. 60 00:04:30,050 --> 00:04:34,070 THE CLOCKS WERE SET TO THE EXACT TIME TO THE CLOCK ON LAND AND 61 00:04:34,070 --> 00:04:38,041 TOGETHER WITH OBSERVING THE MOON, SUN, AND THE CLOCK THEY 62 00:04:38,041 --> 00:04:42,095 COULD DETERMINE THE LONGITUDE AND LATITUDE. 63 00:04:42,095 --> 00:04:46,499 OTHER SHIPS COULD KNOW WHERE THEY WERE GOING. 64 00:04:46,499 --> 00:04:48,301 AMAZING. 65 00:04:48,301 --> 00:04:52,388 HOWEVER, CLOCKS BACK THEN WEREN'T VERY ACCURATE. 66 00:04:52,388 --> 00:04:56,392 IF THE SHIPS DRIFTED OFF FROM THE MAIN CLOCK IT COULD MEAN THE 67 00:04:56,392 --> 00:05:04,200 DIFFERENCE OF FINDING THEIR DESTINATION AND BEING HOPELESSLY 68 00:05:04,200 --> 00:05:04,350 LOST. 69 00:05:04,350 --> 00:05:13,243 TODAY TIME IS PRECISE IN THE GLOBAL POSITIONING SYSTEM OR 70 00:05:13,243 --> 00:05:14,294 GPS. 71 00:05:14,294 --> 00:05:18,431 BOATS, PLANES, CARS REPEAT DATA BACK FROM THE ORBITING SATELLITE 72 00:05:18,431 --> 00:05:24,354 TO CALCULATE THE LONGITUDE AND LATITUDE. 73 00:05:24,354 --> 00:05:28,358 IT ALLOWS YOU TO ARRIVE TO A DESTINATION WITHIN FEET. 74 00:05:28,358 --> 00:05:31,394 IT'S ONLY BECAUSE OF TIME THAT WE CAN KNOW WHERE WE ARE AND 75 00:05:31,394 --> 00:05:40,086 WHERE WE'RE GOING. 76 00:05:40,086 --> 00:05:42,255 WHAT ABOUT IN SPACE? 77 00:05:42,255 --> 00:05:44,440 NOT JUST SPACE BUT DEEP SPACE. 78 00:05:44,440 --> 00:05:50,413 HOW DO YOU NAVIGATE AND EXPLORE A PLACE WHERE THERE ARE NO 79 00:05:50,413 --> 00:05:53,149 LONGITUDE OR LATITUDE. 80 00:05:53,149 --> 00:05:57,403 RIGHT NOW SCIENTISTS NAVIGATE BY USING GIANT ANTENNA HERE ON 81 00:05:57,403 --> 00:05:58,054 EARTH. 82 00:05:58,054 --> 00:06:02,408 NOT THOSE KIND. 83 00:06:02,408 --> 00:06:03,226 THESE KIND. 84 00:06:03,226 --> 00:06:07,046 JUST LIKE THE OLD SEA EXPLORERS. 85 00:06:07,046 --> 00:06:11,301 THESE ANTENNA SEND OUT A SIGNAL BOUNCED OFF THE SPACECRAFT 86 00:06:11,301 --> 00:06:14,020 STRAIGHT BACK TO THE EARTH. 87 00:06:14,020 --> 00:06:23,146 THAT DETERMINES THE SPACECRAFT'S DISTANCE AND SPEED. 88 00:06:23,146 --> 00:06:24,430 THE SIGNALS OF THE SPACECRAFT ARE THE MOST EFFICIENT WAY TO 89 00:06:24,430 --> 00:06:25,331 NAVIGATE SPACE. 90 00:06:25,331 --> 00:06:29,052 THEY CAN ONLY TALK TO ONE SPACECRAFT AT A TIME LEAVING 91 00:06:29,052 --> 00:06:29,419 OTHERS WAITING. 92 00:06:29,419 --> 00:06:35,108 BY THE TIME THE SIGNAL IS CALCULATED AND SENT BACK, THE 93 00:06:35,108 --> 00:06:38,127 SPACECRAFT ISN'T THE SAME SPOT ANYMORE AND THE RESULT HAS TO BE 94 00:06:38,127 --> 00:06:38,311 ADJUSTED. 95 00:06:38,311 --> 00:06:43,249 HOW CAN DEEP SPACE EXPLORATION BECOME EVEN MORE PRECISE. 96 00:06:43,249 --> 00:06:46,469 HOW CAN A PATTERN HAVE A FURTHER AND FURTHER INTO SPACE BE MORE 97 00:06:46,469 --> 00:06:50,290 IMMEDIATE AND INDEPENDENT OF HAVING TO CHECK IN WITH -- 98 00:06:50,290 --> 00:06:53,493 WHAT'S THAT, SAMMY? 99 00:06:53,493 --> 00:06:57,413 OF COURSE, THE DEEP SPACE ATOMIC CLOCK. 100 00:06:57,413 --> 00:07:00,099 ENGINEERS HAVE DEVELOPED A WAY FOR THE SPACECRAFT TO HAVE THE 101 00:07:00,099 --> 00:07:01,050 ON BOARD CLOCK. 102 00:07:01,050 --> 00:07:04,037 IT NO LONGER HAS TO CHECK IN WITH THE COORDINATES. 103 00:07:04,037 --> 00:07:09,409 THIS THE BREAKTHROUGH DEVICE IS SELF-SUFFICIENT AND CAN HANDLE 104 00:07:09,409 --> 00:07:12,462 THE HARSH CONDITIONS OF DEEP SPACE. 105 00:07:12,462 --> 00:07:15,465 NOW THE SPACECRAFT CAN MAKE IMMEDIATE CORRECTIONS ON ITS 106 00:07:15,465 --> 00:07:16,115 OWN. 107 00:07:16,115 --> 00:07:22,222 A MAN WITH INCREDIBLE PRECISION. 108 00:07:22,222 --> 00:07:23,439 FINALLY GETTING HIS DUE. 109 00:07:23,439 --> 00:07:30,413 PAVING THE WAY FOR MORE PRECISE SPACE EXPLORATION. 110 00:07:30,413 --> 00:07:36,169 ONE TICK, TOCK, TICK AT A TIME. 111 00:07:36,169 --> 00:07:47,247 [ APPLAUSE ] >> SO ALLEN AND I ARE GOING TO 112 00:07:47,247 --> 00:07:50,116 ATTEMPT TO ELABORATE A LITTLE BIT FURTHER. 113 00:07:50,116 --> 00:07:56,372 WE CAN BEGIN OUR JOURNEY TALKING ABOUT GOING BACK IN TIME AND 114 00:07:56,372 --> 00:07:57,290 TALKING ABOUT NAVIGATION. 115 00:07:57,290 --> 00:08:00,159 ONE OF THE KEY COMPONENTS OF A NAVIGATION IS MAP. 116 00:08:00,159 --> 00:08:05,248 TO NAVIGATE ON EARTH, MAPS HAVE BEEN DRAWN FOR A MILLENNIA AND 117 00:08:05,248 --> 00:08:10,169 HERE'S AN EXAMPLE OF A MAP DROWN IN 1630. 118 00:08:10,169 --> 00:08:14,374 WHAT IS NOTABLE, IT'S THE FIRST MAP TO IDENTIFY 15 DEGREES OF 119 00:08:14,374 --> 00:08:20,196 LONGITUDE WITH ONE HOUR OF ROTATION OF THE EARTH ABOUT THE 120 00:08:20,196 --> 00:08:20,346 AXIS. 121 00:08:20,346 --> 00:08:25,151 SO HOW WE USE MAPS IS NOT ONLY TO DEFINE, OBVIOUSLY, THE POINTS 122 00:08:25,151 --> 00:08:31,257 OF INTEREST THAT WE WOULD LIKE TO TRAVEL TO, BUT A REFERENCE 123 00:08:31,257 --> 00:08:31,424 SYSTEM. 124 00:08:31,424 --> 00:08:38,448 IN THIS CASE THE LINES ARE LATITUDE AND LINES OF LONGITUDE. 125 00:08:38,448 --> 00:08:43,486 SEA FAIRERS HAVE KNOWN FOR MILLENNIA. 126 00:08:43,486 --> 00:08:52,312 WE CITE THE NORTH STAR. 127 00:08:52,312 --> 00:08:53,413 LONGITUDE IS TRICKIER PROBLEM. 128 00:08:53,413 --> 00:08:57,333 THERE ARE A NUMBER OF METHODS DEVISED OVER THE MANY THOUSANDS 129 00:08:57,333 --> 00:09:00,186 OF YEARS. 130 00:09:00,186 --> 00:09:04,023 THE EARLIEST OF WHICH IS THE SAILORS WOULD DROP A ROPE WITH 131 00:09:04,023 --> 00:09:11,114 KNOTS AT THE BOW OF THE SHIP AND SEE HOW LONG IT TOOK FOR THE 132 00:09:11,114 --> 00:09:14,317 KNOTS TO ARRIVE AT THE STERN OF THE SHIP AND YOU CAN COMPUTE 133 00:09:14,317 --> 00:09:17,070 VELOCITY AND WITH THE TIME YOU CAN COMPUTE DISTANCE. 134 00:09:17,070 --> 00:09:18,321 NOT A VERY ACCURATE METHOD. 135 00:09:18,321 --> 00:09:25,978 AT THE TIME THERE ARE OTHER METHODS, THE MED OF LUNAR 136 00:09:25,978 --> 00:09:26,162 DISTANCES. 137 00:09:26,162 --> 00:09:31,351 IT'S COMPETING WITH USING CLOCKS TO DETERMINE LONGITUDE. 138 00:09:31,351 --> 00:09:36,089 NOW, HOW WE CAN USE A CLOCK TO DETERMINE OUR LONGITUDE IS AT 139 00:09:36,089 --> 00:09:37,206 YOUR POINT DEPARTURE. 140 00:09:37,206 --> 00:09:39,008 LET'S SAY IT'S BRITAIN. 141 00:09:39,008 --> 00:09:42,362 YOUR SET YOUR TIME TO THE GROUND CLOCK THERE. 142 00:09:42,362 --> 00:09:44,364 YOU KNOW THE LONGITUDE BECAUSE YOU HAVE THE MAP AND YOU SET OFF 143 00:09:44,364 --> 00:09:46,265 ON THE TRAVELS. 144 00:09:46,265 --> 00:09:50,386 EACH DAY AT HIGH NOON, YOU CHECK THE TIME ON THE CLOCK. 145 00:09:50,386 --> 00:09:53,156 YOU COMPETE THE DIFFERENCE BETWEEN THAT CLOCK TIME AND HIGH 146 00:09:53,156 --> 00:09:57,226 NOON AND YOU HAVE A MEASURE OF YOUR LONGITUDE DISTANCE YOU HAVE 147 00:09:57,226 --> 00:09:58,478 TRAVELED DURING YOUR TRAVELS. 148 00:09:58,478 --> 00:10:03,449 AND SO THAT, ACTUALLY, IS THE METHOD THAT HAS ESTABLISHED 149 00:10:03,449 --> 00:10:11,290 ITSELF AS A NORM, AT LEAST BACK IN THE 18th CENTURY, AND, IN 150 00:10:11,290 --> 00:10:16,362 FACT, IN 1714, THE BRITISH PARLIAMENT WAS SO DESPERATE TO 151 00:10:16,362 --> 00:10:20,216 FIGURE OUT A SOLUTION TO THE LONGITUDE PROBLEM, THEY SET UP A 152 00:10:20,216 --> 00:10:25,154 PRIZE TO 20,000 POUND TO THE PERSON WHO CAN FIGURE OUT HOW TO 153 00:10:25,154 --> 00:10:26,038 SOLVE THIS. 154 00:10:26,038 --> 00:10:29,525 JOHN HARRISON TOILED FOR DECADES BUILDING MANY CLOCKS. 155 00:10:29,525 --> 00:10:34,313 THE CHALLENGE THAT HE HAD WAS TO TAKE THE ACCURACY OF THE GROUND 156 00:10:34,313 --> 00:10:37,316 CLOCK OF THE DAY, WHICH WERE BIG, AND TRY TO DEVELOP 157 00:10:37,316 --> 00:10:41,187 SOMETHING THAT WAS PORTABLE ON A SHIP THAT COULD WITHSTAND THE 158 00:10:41,187 --> 00:10:44,140 HARSH ENVIRONMENT THAT A SHIP PRESENTS TO A CLOCK'S STABILITY. 159 00:10:44,140 --> 00:10:48,394 SO WHAT I MEAN BY CLOCK STABILITY IS, AS THE CLOCK TICKS 160 00:10:48,394 --> 00:10:52,281 EVERY SECOND, THE CLOCK IS VERY STABLE AT EACH SECOND IT'S THE 161 00:10:52,281 --> 00:10:53,399 SAME LENGTH IN TIME. 162 00:10:53,399 --> 00:10:56,436 IF THAT LENGTH IN TIME VARIES, YOU HAVE AN INSTABILITY. 163 00:10:56,436 --> 00:11:06,262 AND SO ON A SHIP, THINGS LIKE HUMIDITY CHANGES OR MOTION CAN 164 00:11:06,262 --> 00:11:08,064 AFFECT THE STABILITY. 165 00:11:08,064 --> 00:11:11,267 ON THE FOURTH TRY, HE BUILT THIS WATCH RIGHT HERE. 166 00:11:11,267 --> 00:11:17,273 IT'S ABOUT 5 INCHES IN DIAMETER, AND IT WAS SUCCESSFUL AT 167 00:11:17,273 --> 00:11:21,077 ACHIEVING THE OBJECTIVE WITH THE LONGITUDE PRIZE. 168 00:11:21,077 --> 00:11:26,265 1762 A SHIP SET OUT ON A COURSE FROM BRITAIN TO THE WEST INDIES. 169 00:11:26,265 --> 00:11:29,452 IN THAT 62-DAY JOURNEY IT LOST FIVE SECONDS OF TIME. 170 00:11:29,452 --> 00:11:33,456 THE STABILITY OF THAT CLOCK WAS 1/10th OF A SECOND PER DAY AND 171 00:11:33,456 --> 00:11:37,360 THAT YIELDED ABOUT A 2 KILOMETER ERROR LONGITUDE. 172 00:11:37,360 --> 00:11:43,182 THAT WAS GOOD ENOUGH TO NAVIGATE AND SET ABOUT THE WAY IN WHICH 173 00:11:43,182 --> 00:11:47,186 THE MARINERS WOULD FIGURE OUT THE LONGITUDE. 174 00:11:47,186 --> 00:11:51,224 BUT CIVILIZATION EVOLVES AND TECHNOLOGY IMPROVES THE 175 00:11:51,224 --> 00:11:53,276 NAVIGATIONAL NEEDS AND DEMANDS INCREASE. 176 00:11:53,276 --> 00:11:59,081 SO FAST FORWARD TO THE 1960S AND THE NAVY NEEDED A WAY TO FIGURE 177 00:11:59,081 --> 00:12:03,102 OUT WHERE THEIR SHIPS AND SUBMARINES ARE TO MUCH GREATER 178 00:12:03,102 --> 00:12:05,071 ACCURACY THAN PROVIDED. 179 00:12:05,071 --> 00:12:07,373 A SYSTEM WAS BUILD CALLED TRANSIT. 180 00:12:07,373 --> 00:12:10,309 IT'S ABOUT TEN ORBITING SATELLITES. 181 00:12:10,309 --> 00:12:14,163 LOW ALTITUDE ABOUT 1100 KILOMETERS, AND IT WAS DESIGNED 182 00:12:14,163 --> 00:12:18,134 SO THAT AS SATELLITES WOULD OVERFLY THE U.S., THEY WOULD BE 183 00:12:18,134 --> 00:12:18,301 TRACKED. 184 00:12:18,301 --> 00:12:22,305 THOSE TRACKING STATIONS WOULD COMPUTE THE ORBITS OF THE 185 00:12:22,305 --> 00:12:26,392 SPACECRAFT, AND THEN THAT WOULD BE UPLOADED TO THE SPACECRAFT. 186 00:12:26,392 --> 00:12:30,479 WHEN THAT SATELLITE WOULD FLY OVER A SHIP OR SUBMARINE, IT 187 00:12:30,479 --> 00:12:35,384 WOULD SEND A SIGNAL TO THE SHIP OR SUBMARINE AND USING KNOWLEDGE 188 00:12:35,384 --> 00:12:39,088 OF WHERE THE SPACECRAFT WAS AT, BECAUSE IT WOULD BROADCAST THE 189 00:12:39,088 --> 00:12:43,376 LOCATION, IT WOULD MEASURE THE FREQUENCY SHIFT OF THIS SIGNAL 190 00:12:43,376 --> 00:12:47,046 TRANSITTING FROM THE SATELLITE TO THE SHIP. 191 00:12:47,046 --> 00:12:50,449 NOW YOU CAN USE THE INFORMATION TO FIGURE OUT HOW YOUR LOCATION. 192 00:12:50,449 --> 00:12:56,305 BUT WHAT IT REQUIRES IN THIS ONE-WAYAL IS THAT THE CLOCK ON 193 00:12:56,305 --> 00:13:00,109 BOARD THE SATELLITE AND THE CLOCK ON BOARD THE SHIP ARE VERY 194 00:13:00,109 --> 00:13:00,293 ACCURATE. 195 00:13:00,293 --> 00:13:02,311 AND SO THEY WEREN'T GOOD ENOUGH. 196 00:13:02,311 --> 00:13:11,254 TO RESPOND TO THAT, THE TECHNOLOGY FOR CLOCKS SHIFTED TO 197 00:13:11,254 --> 00:13:14,006 USING SOMETHING LIKE A KWAURZ -- QUARTZ CRYSTAL. 198 00:13:14,006 --> 00:13:18,210 HERE IS A PICTURE OF THE USO TRANSIT SATELLITES IN 1960. 199 00:13:18,210 --> 00:13:23,299 AND THE WAY THE QUARTZ CRYSTAL OSCILLATOR WORKS IS THAT IT USES 200 00:13:23,299 --> 00:13:31,357 THE MECHANICAL VIBRATION OF THE QUARTZ TO DO THE TICKING. 201 00:13:31,357 --> 00:13:35,061 THIS DRAMATICALLY IMPROVE THE ACCURACY OF THE NAVIGATION 202 00:13:35,061 --> 00:13:38,314 SYSTEMS ON THE TIME TRANSIT TO DETERMINE THE LOCATION OF A 203 00:13:38,314 --> 00:13:42,501 SHIFT OF ABOUT 200 METERS. 204 00:13:42,501 --> 00:13:44,520 WE USE USO IN DEEP SPACE. 205 00:13:44,520 --> 00:13:51,527 HERE IS A PICTURE OF A USO WE INTEND TO FLY ON OUR MISSION. 206 00:13:51,527 --> 00:13:56,198 THEY'RE OFTEN USED IN DEEP SPACES FOR A LOT OF USES 207 00:13:56,198 --> 00:13:56,399 NAVIGATION. 208 00:13:56,399 --> 00:13:58,050 SOMETIMES, BUT THEY'RE STILL NOT GOOD ENOUGH. 209 00:13:58,050 --> 00:14:03,189 ON OUR MISSION WE BUILT A USO THAT IS STABLE BETTER THAN A 210 00:14:03,189 --> 00:14:04,123 MICROSECOND PER DAY. 211 00:14:04,123 --> 00:14:04,407 IT'S GOOD. 212 00:14:04,407 --> 00:14:08,327 BUT IT'S NOT GOOD ENOUGH FOR DEEP SPACE NAVIGATION. 213 00:14:08,327 --> 00:14:12,031 IN FACT, THE TRANSIT SYSTEM RESPONDED TO THE NEED OF THE 214 00:14:12,031 --> 00:14:15,434 TIME, BUT IT WASN'T GOOD ENOUGH FOR GLOBAL POSITIONING. 215 00:14:15,434 --> 00:14:18,270 WE'RE FAMILIAR WITH THIS CONSTELLATION THAT GLOBAL 216 00:14:18,270 --> 00:14:19,288 POSITIONING SYSTEM. 217 00:14:19,288 --> 00:14:24,193 IT'S A SYSTEM OF 32 SATELLITES, AND THIS RESPONDED TO THE 218 00:14:24,193 --> 00:14:31,200 CHALLENGES PRESENTED BY TRANSIT BY OFFERING MORE COVERAGE 32 219 00:14:31,200 --> 00:14:34,203 SATELLITES YIELD OVER FOUR SATELLITES AT MOST LOCATIONS ON 220 00:14:34,203 --> 00:14:38,074 THE EARTH ALL THE TIME AND OFTEN MORE THAN FOUR SATELLITES. 221 00:14:38,074 --> 00:14:41,460 SO THIS COVERAGE ALLOWS US TO GET POSITIONING TO A MUCH 222 00:14:41,460 --> 00:14:46,032 GREATER ACCURACY THAN A HUNDRED METERS. 223 00:14:46,032 --> 00:14:49,402 AND ANOTHER FUNDAMENTAL ASPECT THERE ARE ATOMIC CLOCKS ON BOARD 224 00:14:49,402 --> 00:14:50,369 THE SPACE SATELLITE. 225 00:14:50,369 --> 00:14:56,509 AND THOSE ATOMIC CLOCKS ARE NEEDED TO ENSURE THAT THE 226 00:14:56,509 --> 00:14:58,227 SIGNALS SENT FROM EACH SATELLITE ARE EXTREMELY PRECISE AND 227 00:14:58,227 --> 00:14:58,411 ACCURATE. 228 00:14:58,411 --> 00:15:02,114 THE FACT THERE ARE 32 SATELLITES MEANS THAT THE USERS CLOCK 229 00:15:02,114 --> 00:15:04,016 DOESN'T NEED TO BE NEARLY AS ACCURATE. 230 00:15:04,016 --> 00:15:05,317 YOU DON'T NEED A USO. 231 00:15:05,317 --> 00:15:08,037 YOU DON'T NEED AN ATOMIC CLOCK. 232 00:15:08,037 --> 00:15:12,074 EVERYBODY WHO HAS A SMARTPHONE HAS A GPS RECEIVER INSIDE THEIR 233 00:15:12,074 --> 00:15:14,360 PHONE, AND THEY DON'T HAVE AN ATOMIC CLOCK. 234 00:15:14,360 --> 00:15:19,081 HOW DO WE DETERMINE OUR POSITION MORE ACCURATELY GIVEN THAT WE 235 00:15:19,081 --> 00:15:22,301 HAVE A WORSE PERFORMING CLOCK THAN OUR PHONE OR OTHER GROUND 236 00:15:22,301 --> 00:15:24,487 GPS RECEIVERS? 237 00:15:24,487 --> 00:15:28,057 SO I'M GOING TO DO A LITTLE EXPERIMENT WITH YOU ALL TO TRY 238 00:15:28,057 --> 00:15:30,126 TO ILLUSTRATE HOW THE PROCESS WORKS. 239 00:15:30,126 --> 00:15:37,066 IT'S A SIMPLIFIED EXAMPLE, BUT THE FUNDAMENTALS ARE TRUE FOR 240 00:15:37,066 --> 00:15:40,419 THE MORE COMPLICATED SITUATIONS WE USE NAVIGATIONAL GPS. 241 00:15:40,419 --> 00:15:45,107 I'M GOING TO FLAT LAND. 242 00:15:45,107 --> 00:15:47,376 A TWO DIMENSIONAL SPACE. 243 00:15:47,376 --> 00:15:50,296 I HAVE THREE GPS SATELLITES INDICATED HERE IN THE CORNER. 244 00:15:50,296 --> 00:15:51,514 I'M SOMEWHERE IN HERE. 245 00:15:51,514 --> 00:15:53,482 I'M TRYING TO FIGURE OUT WHERE I'M AT. 246 00:15:53,482 --> 00:15:58,437 I'M GOING TO TAKE MEASUREMENTS OF MY GPS RECEIVER THAT IS IN MY 247 00:15:58,437 --> 00:15:59,088 PHONE. 248 00:15:59,088 --> 00:16:04,193 THE WAY IT WORKS I'LL GET SIGNALS FROM EACH ONE OF THESE 249 00:16:04,193 --> 00:16:08,114 SATELLITES INSTANTANEOUSLY AND SIMULTANEOUSLY. 250 00:16:08,114 --> 00:16:10,099 WITH THE FIRST MEASUREMENT, I'LL GET A MEASURE OF RANGE. 251 00:16:10,099 --> 00:16:17,356 THE WAY IT WORKS IS THE SATELLITE ESSENTIALLY SEND A 252 00:16:17,356 --> 00:16:19,308 SIGNAL ON THE TIME AND WHEN I RECEIVE IT, WHENEVER I'M AT, 253 00:16:19,308 --> 00:16:26,182 I'LL HAVE A MEASURE OF RANGE AS WELL AS A MEASURE OF HOW FAR OFF 254 00:16:26,182 --> 00:16:27,166 MY LOCAL CLOCK IS. 255 00:16:27,166 --> 00:16:33,072 SO THE GPS SATELLITE IS ABOUT 20,000 KILOMETERS IN ALTITUDE. 256 00:16:33,072 --> 00:16:36,275 IT TAKES ABOUT 70 MILLISECOND FOR THE SIGNAL TO ARRIVE ON 257 00:16:36,275 --> 00:16:36,442 EARTH. 258 00:16:36,442 --> 00:16:43,215 I'M GOING TO COMPARE THAT TIME TO WHAT MY PHONE SAYS AND I'LL 259 00:16:43,215 --> 00:16:46,068 HAVE A MEASURE OF THE DISTANCE PLUS THE AIR IN THE CLOCK. 260 00:16:46,068 --> 00:16:49,371 WITH THE SINGULAR MEASUREMENT, I CAN BE ANYWHERE IN THE BAND 261 00:16:49,371 --> 00:16:52,508 WHERE THE BAND REPRESENTS MY CLOCK HERE. 262 00:16:52,508 --> 00:16:55,311 SO WITH THE SECOND GPS MEASUREMENT, WE HAVE THIS 263 00:16:55,311 --> 00:16:59,348 MEASURE OF RANGE AND I CAN BE ANYWHERE IN THIS BAN. 264 00:16:59,348 --> 00:17:03,185 BUT IF I COMBINE THE TWO, I'M SOMEWHERE IN THE FOOTBALL SHAPED 265 00:17:03,185 --> 00:17:03,402 REGION. 266 00:17:03,402 --> 00:17:07,223 SO I'VE NOW ACTUALLY FIXED MYSELF SOMEWHERE HERE, WHICH IS 267 00:17:07,223 --> 00:17:08,390 TWO MEASUREMENTS. 268 00:17:08,390 --> 00:17:10,242 I STILL DON'T KNOW MY TIME. 269 00:17:10,242 --> 00:17:12,077 I NEED A THIRD MEASUREMENT. 270 00:17:12,077 --> 00:17:17,016 WITH THAT THIRD MEASUREMENT, MY LOCATION GETS MORE PRECISE AND I 271 00:17:17,016 --> 00:17:19,251 HAVE ANOTHER PIECE OF INFORMATION THAT SAYS YOUR 272 00:17:19,251 --> 00:17:24,206 CLOCK'S TIME IS X. 273 00:17:24,206 --> 00:17:27,142 THAT'S, IN A NUTSHELL HOW OUR RECEIVERS IN OUR PHONES AND 274 00:17:27,142 --> 00:17:28,994 OTHER GPS RECEIVERS WORK TODAY. 275 00:17:28,994 --> 00:17:31,347 BUT IT'S STILL NOT GOOD ENOUGH FOR DEEP SPACE NAVIGATION. 276 00:17:31,347 --> 00:17:39,171 WE DON'T HAVE A PLETHORA OF SATELLITES ZRUBTED ACROSS THE 277 00:17:39,171 --> 00:17:41,390 SOLAR SYSTEM TO DID DO THAT NAVIGATION SYSTEM. 278 00:17:41,390 --> 00:17:43,375 WE HAVE THE DEEP SPACE NETWORK. 279 00:17:43,375 --> 00:17:47,179 IT WAS FORMED ABOUT THE TIME THAT NASA WAS FORMED AT THE END 280 00:17:47,179 --> 00:17:51,483 OF THE 1950s, AND THE WAY IN WHICH WE GET TRACKING DATA TO 281 00:17:51,483 --> 00:17:57,156 OUR SATELLITE AND OUR PROBES AND SPACECRAFT ARE THROUGH THE 282 00:17:57,156 --> 00:17:59,291 RATHER HUGE ANTENNA. 283 00:17:59,291 --> 00:18:05,347 THIS PICTURE OVER HERE, THIS IS THE FEED HORN OF THIS 70 METER 284 00:18:05,347 --> 00:18:07,166 ANTENNA IN CALIFORNIA. 285 00:18:07,166 --> 00:18:11,220 THAT'S A PERSON STANDING ON THE END. 286 00:18:11,220 --> 00:18:12,388 THEY'RE BIG. 287 00:18:12,388 --> 00:18:17,192 THE REASON WHY THEY'RE BIG, THEY NEED TO TRANSSUBMIT A POWERFUL 288 00:18:17,192 --> 00:18:19,461 SYSTEM TO SPACECRAFT IN SATELLITES THAT ARE HUNDRED OF 289 00:18:19,461 --> 00:18:21,080 MILLIONS OF KILOMETERS AWAY. 290 00:18:21,080 --> 00:18:25,200 THE SATELLITES DON'T HAVE THE TRANSMISSION POWER TO RETURN IT. 291 00:18:25,200 --> 00:18:29,305 THESE ANTENNAS -- EXCUSE ME, THEY HAVE THE POWER TO RETURN 292 00:18:29,305 --> 00:18:29,438 IT. 293 00:18:29,438 --> 00:18:32,207 THEY HAVE HIGH GAIN ANTENNA ON THEM AS WELL. 294 00:18:32,207 --> 00:18:40,115 BUT IT STARTS WITH A LARGE TRANSMISSION FROM ONE OF THE 295 00:18:40,115 --> 00:18:40,299 STATIONS. 296 00:18:40,299 --> 00:18:46,372 YOU CAN IMAGINE THERE ARE ONLY THREE COMPLEXES ON EARTH. 297 00:18:46,372 --> 00:18:52,011 THEY'RE SEPARATED LONGITUDELY BY 122 DEGREES SO TYPICALLY THERE'S 298 00:18:52,011 --> 00:18:56,165 ALWAYS ONE STATION IN VIEW OF A SPACECRAFT OR SPACECRAFT IN THE 299 00:18:56,165 --> 00:18:58,100 SOLAR SYSTEM. 300 00:18:58,100 --> 00:19:01,120 AND THE WAY IN WHICH THIS SYSTEM WORKS IT USES RANGING LIKE THE 301 00:19:01,120 --> 00:19:04,240 GPS, BUT WE USE TWO-WAY RANGING, TYPICALLY, TODAY. 302 00:19:04,240 --> 00:19:08,961 AND THE REASON WE USE TWO-WAY RANGING AND DOPPLER IS THAT THE 303 00:19:08,961 --> 00:19:11,130 SPACECRAFT CLOCKS AREN'T GOOD ENOUGH. 304 00:19:11,130 --> 00:19:15,301 AT BEST THEY HAVE USO TODAY. 305 00:19:15,301 --> 00:19:18,120 AND THOSE AREN'T STABLE ENOUGH SO THAT THE ONE-WAY SIGNALS WE 306 00:19:18,120 --> 00:19:22,358 GET WITH THEM WILL ALLOW US TO NAVIGATE ACCURATELY AND 307 00:19:22,358 --> 00:19:23,058 PRECISELY. 308 00:19:23,058 --> 00:19:28,213 SO THE WAY THE TWO-WAY SIGNAL WORKS IS THEY'LL SEND THAT TONE 309 00:19:28,213 --> 00:19:29,164 AT A CERTAIN TIME. 310 00:19:29,164 --> 00:19:31,283 IT WILL SEND IT UP TO THE SPACECRAFT. 311 00:19:31,283 --> 00:19:36,405 THE SPACECRAFT WILL TURN IT AROUND AND BE RECEIVED BACK HERE 312 00:19:36,405 --> 00:19:39,391 AT EARTH AND THAT'S WHERE THE MEASUREMENT TAKES PLACE. 313 00:19:39,391 --> 00:19:43,112 ON THE GROUND WE'LL PROCESS THE DATA TO FIGURE OUT THE 314 00:19:43,112 --> 00:19:44,196 TRAJECTORY OF THE SPACECRAFT. 315 00:19:44,196 --> 00:19:48,334 NOW YOU CAN IMAGINE THAT YOU NEED PRECISION CLOCKS AND 316 00:19:48,334 --> 00:19:50,035 FREQUENCY SOURCES IN THE STATIONS. 317 00:19:50,035 --> 00:19:51,070 WE DO. 318 00:19:51,070 --> 00:19:54,490 WE HAVE VERY PRECISE STABLE STANDARDS. 319 00:19:54,490 --> 00:19:59,094 ALAN WILL TALK TO YOU AND SHOW YOU PICTURES OF HOW BIG THEY 320 00:19:59,094 --> 00:19:59,228 ARE. 321 00:19:59,228 --> 00:20:00,362 THEY'RE STABLE AND PRECISE. 322 00:20:00,362 --> 00:20:05,451 THEY ONLY DRIFT ABOUT A TENTH OF A MECHANIC KNOW SECOND PER DAY. 323 00:20:05,451 --> 00:20:07,286 IT'S A EXTREMELY TINY NUMBER. 324 00:20:07,286 --> 00:20:09,488 THIS IS GOOD ENOUGH FOR DEEP SPACE NAVIGATION. 325 00:20:09,488 --> 00:20:14,276 I'M GOING TO DO ANOTHER EXPERIMENT AND ILLUSTRATE HOW WE 326 00:20:14,276 --> 00:20:22,067 DO DEEP SPACE NAVIGATION WITH THESE KINDS OF SIGNALS. 327 00:20:22,067 --> 00:20:27,072 WE HAVE TO KEEP IN MIND ABOUT THE EARTH-BASED AND A HALF 328 00:20:27,072 --> 00:20:27,272 NAVIGATION. 329 00:20:27,272 --> 00:20:28,440 WE'RE IN THE SOLAR SYSTEM. 330 00:20:28,440 --> 00:20:30,442 WE HAVE TO FIGURE OUT WHAT WE NEED. 331 00:20:30,442 --> 00:20:32,177 IT'S A REFERENCE SYSTEM. 332 00:20:32,177 --> 00:20:34,313 ON EARTH WE HAVE LATITUDE AND LONGITUDE. 333 00:20:34,313 --> 00:20:40,069 IN DEEP SPACE WE HAVE A THREE DIMENSIONAL SYSTEM WE DEFINE AT 334 00:20:40,069 --> 00:20:41,103 THE CENTER NEAR THE CENTER OF THE SUN. 335 00:20:41,103 --> 00:20:44,139 WE NEED A MAP. 336 00:20:44,139 --> 00:20:46,342 WE NEED A MAP OF WHERE THE DESTINATIONS ARE. 337 00:20:46,342 --> 00:20:49,511 THE TRAJECTORIES OF THE PLANETS AND MOONS ANDS A STROIDS. 338 00:20:49,511 --> 00:20:54,416 WITH THIS MAP AND THIS SYSTEM AND THE TRACKING DATA, WE CAN 339 00:20:54,416 --> 00:21:01,457 RESOLVE LOCATIONS AND TRAJECTORIES AND SPACECRAFT. 340 00:21:01,457 --> 00:21:07,079 UNLIKE GPS WHERE WE DIDN'T NEED PRECISION MODELS OF HOW 341 00:21:07,079 --> 00:21:08,013 SPACECRAFT MOVES. 342 00:21:08,013 --> 00:21:13,218 BECAUSE OF ONLY HAVING A SINGLE STATION AT ANY GIVEN TIME, WE 343 00:21:13,218 --> 00:21:16,472 NEED PRECISE MODELS OF HOW SPACECRAFT MOVEMENTS FACE. 344 00:21:16,472 --> 00:21:21,443 FOR THOSE THAT HAD A COLLEGE PHYSICS CLASS, THESE ARE THE 345 00:21:21,443 --> 00:21:24,079 EQUATIONS OF MOTION YOU WERE TAUGHT BACK IN THAT DAY. 346 00:21:24,079 --> 00:21:30,169 THERE A NUMBER OF FORCES THAT ARE TRANSITING THROUGH THE SOLAR 347 00:21:30,169 --> 00:21:30,369 SYSTEM. 348 00:21:30,369 --> 00:21:35,390 OF COURSE, THE GRAVITATIONAL PARTS OF THE PLANETS NEED TO BE 349 00:21:35,390 --> 00:21:36,108 ACCOUNTED FOR. 350 00:21:36,108 --> 00:21:39,078 THE FACT THAT THE GRAVITY FEEL THAT ANY GIVEN PLANET IS 351 00:21:39,078 --> 00:21:42,247 NONUNIFORM TUGS ON THE SPACECRAFT. 352 00:21:42,247 --> 00:21:45,084 THE FACT THAT THE SUN BEAMS ENERGY ON THE SPACECRAFT PUSHES 353 00:21:45,084 --> 00:21:46,518 IT AROUND, TOO. 354 00:21:46,518 --> 00:21:48,087 WE NEED TO ACCOUNT FOR THAT. 355 00:21:48,087 --> 00:21:51,223 WE NEED TO ACCOUNT FOR THE FACT THAT SPACE ISN'T FLAT. 356 00:21:51,223 --> 00:21:54,209 EINSTEIN TOLD US IT'S CURVED. 357 00:21:54,209 --> 00:21:58,363 SO TIME WILL CHANGE ITS RATE BASED ON WHERE WE'RE AT IN THE 358 00:21:58,363 --> 00:22:01,416 GRAVITY WALLS OF EACH OF THESE SOLAR SYSTEM BODIES. 359 00:22:01,416 --> 00:22:03,085 WE HAVE TO ACCOUNT FOR THAT. 360 00:22:03,085 --> 00:22:08,240 WE HAVE TO ACCOUNT FOR GASES THAT ARE EMANATING FROM OUR 361 00:22:15,047 --> 00:22:08,440 SPACECRAFT. 362 00:22:15,047 --> 00:22:17,132 WE COUPLE IT WITH THE TRACKING DATA WE GET. 363 00:22:17,132 --> 00:22:19,134 THIS IS HOW IT WORKS. 364 00:22:19,134 --> 00:22:25,407 AT LEAST IN THE LITTLE TWO-DAY EXAMPLE, AND NOW, LIKE BEFORE, I 365 00:22:25,407 --> 00:22:30,479 HAVE A SPACE WITH THE REFERENCE SYSTEM, AND THIS EXAMPLE I'M 366 00:22:30,479 --> 00:22:35,300 GOING IT LOOK AT ONE WAY DATA WITH A BAD CLOCK. 367 00:22:35,300 --> 00:22:36,451 WE DON'T HAVE THAT NOW. 368 00:22:36,451 --> 00:22:41,156 AND I HAVE A SINGLE STATION IS IN VIEW OF THE SATELLITE AND THE 369 00:22:41,156 --> 00:22:46,178 OTHER THING I KNOW IN THIS LITTLE EXPERIMENT IS I'M ON A 370 00:22:46,178 --> 00:22:50,449 TRAJECTORY THAT IS A STRAIGHT LINE TRAVELING AT A CONSTANT 371 00:22:50,449 --> 00:22:51,166 VELOCITY. 372 00:22:51,166 --> 00:22:53,418 IT'S A KEY INFORMATION FOR IT TO WORK. 373 00:22:53,418 --> 00:22:57,272 IT WILL GET THE FIRST MEASUREMENT TO MY SPACECRAFT. 374 00:22:57,272 --> 00:23:04,279 TO MEASURE OF RANGE AND, LIKE BEFORE, I CAN BE ANYWHERE ON 375 00:23:04,279 --> 00:23:05,013 THAT CURVE. 376 00:23:05,013 --> 00:23:08,233 IT'S THE SAME RANGE AS HERE AS HERE. 377 00:23:08,233 --> 00:23:12,304 THE BAN REPRESENTS THIS. 378 00:23:12,304 --> 00:23:15,073 I GET ANOTHER ONE AT SOME LATER TIME. 379 00:23:15,073 --> 00:23:17,459 IT'S NOT FOUR MEASUREMENTS AT THE SAME TIME, IT'S AT A 380 00:23:17,459 --> 00:23:20,062 DIFFERENT TIME. 381 00:23:20,062 --> 00:23:20,312 SO I'VE MOVED. 382 00:23:20,312 --> 00:23:23,131 AND SO NOW THE RANGE TO THE SPACECRAFT HAS CHANGED. 383 00:23:23,131 --> 00:23:25,450 AND I CAN BE ANYWHERE HERE. 384 00:23:25,450 --> 00:23:30,038 AND I CAN TAKE ANOTHER ONE AND ANOTHER ONE. 385 00:23:30,038 --> 00:23:32,090 I HAVE FOUR PIECES OF INFORMATION NOW. 386 00:23:32,090 --> 00:23:35,194 AND FOR MY SIMPLE MODEL OF A STRAIGHT LINE MOTION WITH A 387 00:23:35,194 --> 00:23:36,094 CONSTANT VELOCITY. 388 00:23:36,094 --> 00:23:38,113 THAT'S ENOUGH TO FIGURE OUT WHERE I'M AT. 389 00:23:38,113 --> 00:23:39,097 I HAVE A PROBLEM. 390 00:23:39,097 --> 00:23:41,416 I HAVE THIS LARGE CLOCK HERE. 391 00:23:41,416 --> 00:23:43,285 I CAN PICK A SOLUTION LIKE THIS. 392 00:23:43,285 --> 00:23:51,276 AND THIS IS PERFECTLY SATISFACTIONLY. 393 00:23:51,276 --> 00:23:53,245 BOTH OF THESE SOLUTIONS ARE WRONG. 394 00:23:53,245 --> 00:23:55,247 THE RIGHT SOLUTION IS THAT. 395 00:23:55,247 --> 00:23:59,084 BUT MY DATA IS NOT GOOD ENOUGH TO TELL ME THAT SOLUTION. 396 00:23:59,084 --> 00:24:02,020 SO LET'S SWITCH THE SCENARIO A LITTLE BIT. 397 00:24:02,020 --> 00:24:04,006 NOW WE'RE GETTING TWO-WAY DATA. 398 00:24:04,006 --> 00:24:05,407 THAT'S THE WAY WE DO TODAY. 399 00:24:05,407 --> 00:24:11,296 WE'RE GETTING ONE-WAY DATA ON BOARD THAT SPACECRAFT. 400 00:24:11,296 --> 00:24:15,033 SAME THING WE GET OUR FIRST RANGE MEASUREMENT, OUR SECOND, 401 00:24:15,033 --> 00:24:16,368 THIRD, AND FOURTH. 402 00:24:16,368 --> 00:24:20,355 BUT NOW YOU'LL NOTICE THAT MY LINE IS VERY NARROW. 403 00:24:20,355 --> 00:24:23,392 THAT'S BECAUSE MY CLOCK IS VERY ACCURATE. 404 00:24:23,392 --> 00:24:26,194 OR MY TWO-WAY MEASUREMENT IS ACCURATE. 405 00:24:26,194 --> 00:24:31,300 THE ONE-WAY DATA IS AS ACCURATE AS THE TWO-WAY DATA WE GET 406 00:24:31,300 --> 00:24:31,466 TODAY. 407 00:24:31,466 --> 00:24:33,168 NOW I'M GOING SET MY LINE. 408 00:24:33,168 --> 00:24:34,419 I KNOW IT'S A STRAIGHT LINE. 409 00:24:34,419 --> 00:24:37,189 I KNOW IT'S A CONSTANT VELOCITY. 410 00:24:37,189 --> 00:24:39,391 THAT'S THE ONLY LINE THAT WORKS IN THIS LITTLE EXAMPLE. 411 00:24:39,391 --> 00:24:44,246 AND THE REASON WHY IT WORKS IS BECAUSE I HAVE THIS PRECISION 412 00:24:44,246 --> 00:24:48,300 MEASUREMENT OF RANGE. 413 00:24:48,300 --> 00:24:51,470 YOU CAN IMAGINE IT'S A SIMPLE EXACT. 414 00:24:51,470 --> 00:24:53,372 IT'S MORE COMPLICATED IN REAL LIFE. 415 00:24:53,372 --> 00:24:56,108 BUT FUNDAMENTALLY THIS IS HOW IT WORKS. 416 00:24:56,108 --> 00:25:00,445 WHAT DOES IT MEAN FOR THE FUTURE OF NAVIGATION IN DEEP SPACE? 417 00:25:00,445 --> 00:25:04,349 THIS IS A WAY IT WORKS TODAY. 418 00:25:04,349 --> 00:25:06,385 SO I'VE CHOSEN ANOTHER EXAMPLE TO ILLUSTRATE THE FLEXIBILITY 419 00:25:06,385 --> 00:25:14,226 AND THE SCALEABILITY THAT D SACK IMPLIES FOR THE DEEP SPACE 420 00:25:14,226 --> 00:25:14,426 NAVIGATION. 421 00:25:14,426 --> 00:25:19,464 WE HAVE A LOT OF ORBITERS AND ROVERERS ON THE SURFACE OF MARRS 422 00:25:19,464 --> 00:25:20,132 TODAY. 423 00:25:20,132 --> 00:25:21,333 HERE IS AN EXAMPLE. 424 00:25:21,333 --> 00:25:23,435 WE'VE GOT FOUR ORBITERS AT MARRS. 425 00:25:23,435 --> 00:25:29,408 WE HAVE A SPACECRAFT THAT IS GOING TO LAND ON MARS. 426 00:25:29,408 --> 00:25:32,344 WE'RE GOING TO TRACK IT USING TWO-WAY TRACKING. 427 00:25:32,344 --> 00:25:36,298 TODAY YOU HAVE AN TEN THAT, AND IT WILL COMMUNICATE WITH THE 428 00:25:36,298 --> 00:25:38,367 SPACECRAFT AND GET THE TWO-WAY TRACKING. 429 00:25:38,367 --> 00:25:43,155 BECAUSE OF THE TWO-WAY LENGTH IT'S THE ONLY VEHICLE THAT IS 430 00:25:43,155 --> 00:25:44,373 GETTING IN TRACKING. 431 00:25:44,373 --> 00:25:51,096 SO TO GET TRACKING ON THAT ORBITER, YOU NEED ANOTHER 432 00:25:51,096 --> 00:25:52,197 ANTENNA. 433 00:25:52,197 --> 00:25:53,448 UNFORTUNATELY THEY AREN'T GETTING ANY TRACKING. 434 00:25:53,448 --> 00:25:54,366 THEY HAVE THE TIMESHARE. 435 00:25:54,366 --> 00:26:01,206 ALL THE VEHICLES AT D-SACK AND USING ONE-WAY TRACKING QUESTION 436 00:26:01,206 --> 00:26:04,042 TAKE ADVANTAGE THAT THEY CAN LISTEN TO MORE THAN ONE 437 00:26:04,042 --> 00:26:05,143 SPACECRAFT AT THE TIME. 438 00:26:05,143 --> 00:26:08,263 THEY CAN LISTEN TO TWO AND THERE ARE PLANS TO UPGRADE TO FOUR. 439 00:26:08,263 --> 00:26:13,418 IN THIS EXAMPLE, THE SPACECRAFT AND THAT SPACECRAFT CAN GET THE 440 00:26:13,418 --> 00:26:20,042 NEEDED TRACKING FOR ORBIT DETERMINATION OR NAVIGATION. 441 00:26:20,042 --> 00:26:23,311 IN FACT, THIS ANTENNA THERE'S AN ANTENNA BROADCASTING TO MARS. 442 00:26:23,311 --> 00:26:26,048 YOU CAN TRACK A SIGNAL ON THE UP LENGTH. 443 00:26:26,048 --> 00:26:30,218 WHAT IS NEAT ABOUT THIS TRACKING IT'S LIKE A BROADCAST SIGNAL 444 00:26:30,218 --> 00:26:34,272 LIKE GPS OR TRANSIT. 445 00:26:34,272 --> 00:26:39,094 IT DOESN'T REQUIRE THIS SATELLITE TO TALK BACK. 446 00:26:39,094 --> 00:26:42,114 SO ANYBODY LISTENING IN CAN GET ONE-WAY TRACKING. 447 00:26:42,114 --> 00:26:45,233 THAT'S GOOD ENOUGH FOR NAVIGATION. 448 00:26:45,233 --> 00:26:48,070 AND FURTHER MORE, THIS IS LEADING TO THE LATTER PART OF 449 00:26:48,070 --> 00:26:52,190 THE TALK IS NOT ONLY COULD YOU COLLECT THAT DATA ON BOARD, NOW 450 00:26:52,190 --> 00:26:58,413 YOU HAVE THE POSSIBILITY OF PROCESSING IT ON BOARD. 451 00:26:58,413 --> 00:27:04,069 SO I'M GOING LET ALLEN TALK NOW ABOUT HOW ATOMIC CLOCKS WORK. 452 00:27:04,069 --> 00:27:09,307 WHEN HE'S DONE WE'LL TALK ABOUT HOW IT CAN BE USED FOR FUTURE 453 00:27:09,307 --> 00:27:11,193 NAVIGATION AND EXPLORATION. >> THANK YOU. 454 00:27:11,193 --> 00:27:14,379 THIS IS NOT AN ATOMIC CLOCK. 455 00:27:14,379 --> 00:27:16,114 THIS IS SUN DIAL. 456 00:27:16,114 --> 00:27:20,185 SUN DIALS HAVE BEEN USED FOR THE LAST 2700 YEARS, AS FAR AS WE 457 00:27:20,185 --> 00:27:23,188 CAN TELL, PROBABLY EVEN EARLIER THAN THAT. 458 00:27:23,188 --> 00:27:27,109 UNTIL THE 1800 SUN DIALS WERE CONSIDERED THE CORRECT TIME. 459 00:27:27,109 --> 00:27:30,462 EVEN THOUGH WE HAD PENDULUM CLOCKS AFTER THAT. 460 00:27:30,462 --> 00:27:42,107 UNTIL THE 1800S PENDULUM CLOCKS WEREN'T CONSIDERED ACCURATE 461 00:27:42,107 --> 00:27:47,245 ENOUGH. 462 00:27:47,245 --> 00:27:48,396 THERE'S A LOT OF SUN DIALS. 463 00:27:48,396 --> 00:27:52,033 THERE ARE MORE SUN DIALS THAN TYPES OF CLOCKS, PROBABLY. 464 00:27:52,033 --> 00:27:55,253 THEY WERE INVENTED OVER THE CENTURIES TO SOLVE PROBLEMS AS 465 00:27:55,253 --> 00:27:59,157 SUN DIALS HAVE LIKE THEIR ACCURACY VARIES WITH THE TIME OF 466 00:27:59,157 --> 00:27:59,307 YEAR. 467 00:27:59,307 --> 00:28:04,329 BECAUSE THE EARTH IS NOT IN A CIRCULAR ORBIT AROUND THE SUN. 468 00:28:04,329 --> 00:28:06,148 IT'S ACTUALLY AN ELLIPSE. 469 00:28:06,148 --> 00:28:12,170 AND THE SHADOW MOVES AROUND A LITTLE BIT. 470 00:28:12,170 --> 00:28:20,378 IN THE 1800S OR THE CHRISTIAN -- THE SAME OF SATURN AND TIE TAN 471 00:28:20,378 --> 00:28:26,234 FAME INVENTED THE FIRST PRACTICAL PENDULUM CLOCK IN THE 472 00:28:26,234 --> 00:28:27,152 1600s. 473 00:28:27,152 --> 00:28:31,139 THESE CLOCKS WORK BY MEASURING HOW MUCH TIME IT TAKES FOR 474 00:28:31,139 --> 00:28:32,073 PENDULUMS TO SWING. 475 00:28:32,073 --> 00:28:35,310 THAT'S A THING THAT IS A PROPERTY. 476 00:28:35,310 --> 00:28:39,164 OF PENDULUMS IT DOESN'T MATTER HOW HEAVY THEY ARE IT MATTERS 477 00:28:39,164 --> 00:28:40,248 HOW LONG THEY ARE. 478 00:28:40,248 --> 00:28:44,319 AND IT DETERMINES HOW MUCH TIME THEY TAKE TO SWING BACK AND 479 00:28:44,319 --> 00:28:44,469 FORTH. 480 00:28:44,469 --> 00:28:46,404 IT'S AN EXAMPLE OF AN ABSOLUTE CLOCK. 481 00:28:46,404 --> 00:28:49,124 YOU DON'T HAVE TO DO ANY ADDING. 482 00:28:49,124 --> 00:28:51,359 JUST READ OFF THE FACE WHAT TIME IT IS. 483 00:28:51,359 --> 00:28:55,063 A PENDULUM CLOCK YOU HAVE TO ADD UP THE SWINGS. 484 00:28:55,063 --> 00:28:57,432 LIKE YOU HEARD TODD TALKING ABOUT THE BARS BEING WIDE, THE 485 00:28:57,432 --> 00:29:00,352 CLOCKS WHERE YOU HAVE TO ADD UP THE SWINGS HAVE ERRORS. 486 00:29:00,352 --> 00:29:05,991 AND EVERY TIME YOU ADD THE SWINGS TOGETHER YOU ADD MORE AND 487 00:29:05,991 --> 00:29:06,341 MORE ERRORS. 488 00:29:06,341 --> 00:29:10,395 PENDULUMS WERE NOT GOOD ENOUGH UNTIL THEY WERE ENGINEERED TO BE 489 00:29:10,395 --> 00:29:14,432 BETTER THAN SUN DIALS ONLY ABOUT 200 YEARS AGO. 490 00:29:14,432 --> 00:29:25,310 SO AFTER PENDULUM CLOCKS IN THE 1920s, QUARTZ CRYSTAL CLOCK WAS 491 00:29:25,310 --> 00:29:26,044 INCONVENIENTED. 492 00:29:26,044 --> 00:29:30,148 IT'S THE PROBABLY IN THE WRISTWATCH OR ALARM CLOCK. 493 00:29:30,148 --> 00:29:32,017 IF YOU STILL HAVE ONE. 494 00:29:32,017 --> 00:29:33,435 EVERYBODY USES THEIR PHONES NOW. 495 00:29:33,435 --> 00:29:37,305 THEY RELY ON A DIFFERENT PRINCIPLE THAN A PENDULUM. 496 00:29:37,305 --> 00:29:41,226 IT'S A LITTLE PIECE OF ROCK, QUARTZ, WHEN IT'S PLACED IN AN 497 00:29:41,226 --> 00:29:43,194 ELECTRICITY FIELD IT VIBRATES. 498 00:29:43,194 --> 00:29:45,363 BECAUSE OF THE SHAPE, IT'S PRECISELY SHAPED. 499 00:29:45,363 --> 00:29:49,251 BECAUSE OF THE SHAPE, IT ONLY VIBRATES AT A CERTAIN FREQUENCY 500 00:29:49,251 --> 00:29:51,169 OR CERTAIN NUMBER OF TICKS. 501 00:29:51,169 --> 00:29:56,241 JUST LIKE A PENDULUM CLOCK, A KWAURDS CLOCK, WHICH IS AN ORDER 502 00:29:56,241 --> 00:29:59,177 MAGNITUDE OVER TEN TIMES MORE ACCURATE THAN A PENDULUM CLOCK. 503 00:29:59,177 --> 00:30:01,046 IT'S ADDING UP THE TICKS. 504 00:30:01,046 --> 00:30:04,249 AS TODD SAID IT'S NOT GOOD ENOUGH FOR NAVIGATION. 505 00:30:04,249 --> 00:30:08,219 SO WE MOVE INTO ATOMIC CLOCKS. 506 00:30:08,219 --> 00:30:09,404 AND AN ATOMIC CLOCK. 507 00:30:09,404 --> 00:30:12,374 IT'S A CLASSIC ATOMIC CLOCK. 508 00:30:12,374 --> 00:30:13,241 THIS IS A CLOCK. 509 00:30:13,241 --> 00:30:18,330 IT'S A TYPE OF CLOCK USED IN REFERENCE CLOCKS AND TELEVISION 510 00:30:18,330 --> 00:30:22,050 STATIONS, BANKS, IN BANKS, YES. 511 00:30:22,050 --> 00:30:23,285 THEY DO TIME EVERYTHING. 512 00:30:23,285 --> 00:30:26,154 AND ALL OVER THE WORLD. 513 00:30:26,154 --> 00:30:31,426 BANKS ARE USED TOGETHER TO CREATE WHAT WE USUALLY REFER TO 514 00:30:31,426 --> 00:30:33,295 AS UNIVERSAL COORDINATED TIME. 515 00:30:33,295 --> 00:30:35,347 THEY'RE KNOWN AS PRIMARY STANDARD. 516 00:30:35,347 --> 00:30:36,431 THEY DON'T VARY MUCH AT ALL. 517 00:30:36,431 --> 00:30:38,249 WHAT IS AN ATOMIC CLOCK? 518 00:30:38,249 --> 00:30:41,403 IT'S ATOMIC BUT IT'S NOT ATOMIC LIKE THIS. 519 00:30:41,403 --> 00:30:44,205 THIS IS ACTUALLY IS CALLED A NUCLEAR. 520 00:30:44,205 --> 00:30:46,474 AN ATOMIC CLOCK IS AN ATOMIC DEVICE. 521 00:30:46,474 --> 00:30:52,330 BUT THEY SHARE THE SAME HERITAGE AND THEY CAME ABOUT AT ROUGHLY 522 00:30:52,330 --> 00:30:56,167 THE SAME TIME IN THE '40s. 523 00:30:56,167 --> 00:30:57,552 WE USE A MERCURY TRAP CLOCK. 524 00:30:57,552 --> 00:31:00,105 AND I'M GOING TO TELL YOU ABOUT THAT A LITTLE BIT. 525 00:31:00,105 --> 00:31:04,059 THERE ARE OTHER TYPES OF ATOMIC CLOCKS, BUT THE PRINCIPLE IS 526 00:31:04,059 --> 00:31:08,396 REASONABLY THE SAME EVEN THOUGH THE DETAILS ARE IMMENSELY MORE 527 00:31:08,396 --> 00:31:11,282 COMPLEX DEPENDING ON THE DIFFERENT ONES. 528 00:31:11,282 --> 00:31:13,201 WE USE A MERCURY AT TOM HERE. 529 00:31:13,201 --> 00:31:17,022 IT HAS 80 ELECTRONS SPINNING AROUND IN THE SHELLS. 530 00:31:17,022 --> 00:31:20,308 THE ONE WE CARE ABOUT IS THE TWO ON THE OUTSIDE SHELL BECAUSE 531 00:31:20,308 --> 00:31:22,494 THOSE ARE THE ONES WE INTERACT WITH. 532 00:31:22,494 --> 00:31:28,083 AND WE IONIZE THESE, WHICH MEANS WE USE AN ELECTRIC CURRENT TO 533 00:31:28,083 --> 00:31:30,285 KNOCK OFF THE ELECTRON. 534 00:31:30,285 --> 00:31:32,103 THEN WE ONLY WORRY ABOUT THE ONE. 535 00:31:32,103 --> 00:31:33,455 WE CALL IT MERCURY AT TOM. 536 00:31:33,455 --> 00:31:39,227 WE REFER TO IT AS A QUANTUM TUNING FORK. 537 00:31:39,227 --> 00:31:42,497 IT WILL RESPOND TO CERTAIN RADIO SIGNALS. 538 00:31:42,497 --> 00:31:44,532 BUT ONLY CERTAIN ONES. 539 00:31:44,532 --> 00:31:47,068 SO THIS IS OUR TUNING FORK. 540 00:31:47,068 --> 00:31:53,074 WHAT WE DO IS WE SEND A RADIO FREQUENCY AT THIS AT TOM, AND 541 00:31:53,074 --> 00:31:56,394 THIS RADIO FREQUENCY INTERACTS WITH THE ELECTRON. 542 00:31:56,394 --> 00:32:07,122 IF THE FREQUENCY IS NOT RIGHT, THE TUNING FORK DOESN'T DO 543 00:32:07,122 --> 00:32:07,305 ANYTHING. 544 00:32:07,305 --> 00:32:08,139 THE ATOM IS NOT PER TRUSHED. 545 00:32:08,139 --> 00:32:09,224 IF IT'S FASTER IT WILL VIBRATE WITH IT. 546 00:32:09,224 --> 00:32:12,177 IT'S NOT VIBRATING. 547 00:32:12,177 --> 00:32:15,246 IT'S DOING A MAGNETIC PULL NUCLEAR SPIN THING. 548 00:32:15,246 --> 00:32:21,386 IF THE FREQUENCY IS EXACTLY 40.5 AND ABOUT 50 DECIMAL POINTS 549 00:32:21,386 --> 00:32:26,224 FREQUENCY, THIS ATOM WILL REACT IN A WAY WE CAN MEASURE WITH 550 00:32:26,224 --> 00:32:29,194 ULTRA VIOLET LIGHT. 551 00:32:29,194 --> 00:32:32,514 ONE OF THE DIFFICULTIES WITH ATOMIC CLOCKS THE ATOMS ARE NOT 552 00:32:32,514 --> 00:32:35,383 JUST AFFECTED BY THE FREQUENCY YOU'RE HITTING THEM WITH. 553 00:32:35,383 --> 00:32:37,469 THEY'RE AFFECTED BY THE WORLD AROUND THEM. 554 00:32:37,469 --> 00:32:40,405 WE TRY TO DISCONNECT THEM FROM THE UNIVERSE. 555 00:32:40,405 --> 00:32:42,457 WE DO THAT BY TRAPPING THEM. 556 00:32:42,457 --> 00:32:48,096 AND SO WE PUT THEM INSIDE THIS LITTLE DEVICE WHICH IS ABOUT THE 557 00:32:48,096 --> 00:32:49,414 SIZE OF A THREE MUSKETEERS BAR. 558 00:32:49,414 --> 00:32:50,398 THE BIG BAR. 559 00:32:50,398 --> 00:32:54,085 NOT THE BITE SIZE ONE. 560 00:32:54,085 --> 00:32:57,355 WE BASICALLY INSIDE THE GOLD RODS HERE WE FORM AN ELECTRIC 561 00:32:57,355 --> 00:33:01,242 FIELD AND PUT A BUNCH OF MERCURY ATOMS IN THERE. 562 00:33:01,242 --> 00:33:04,129 WE IONIZE THEM AND THEY STAY IN A BOTTLE. 563 00:33:04,129 --> 00:33:05,230 THEY'RE IN THE LITTLE BOTTLE. 564 00:33:05,230 --> 00:33:07,482 THEY DON'T INTERACT WITH THE METAL. 565 00:33:07,482 --> 00:33:10,318 THEY DON'T BOUNCE OFF ANYTHING. 566 00:33:10,318 --> 00:33:12,270 THEY FLY AROUND IN LAZY CIRCLES. 567 00:33:12,270 --> 00:33:14,305 AND IT MAKES THEM VERY QUALM. 568 00:33:14,305 --> 00:33:19,194 WHEN THEY'RE CALM THEY CAN REACT VERY NICELY TO THE RADIO WAVES 569 00:33:19,194 --> 00:33:24,082 THAT WE PUMP IN INTO THE PORTS HERE. 570 00:33:24,082 --> 00:33:24,232 OKAY. 571 00:33:24,232 --> 00:33:31,256 NOW YOU MIGHT THINK, OKAY, IT'S MERCURY. 572 00:33:31,256 --> 00:33:35,410 IS IT DANGEROUS? 573 00:33:35,410 --> 00:33:37,295 THE AMOUNT OF MERCURY WE HAVE. 574 00:33:37,295 --> 00:33:40,415 THERE'S MORE MERCURY IN TWO CANS OF TUNA FISH. 575 00:33:40,415 --> 00:33:47,222 THERE'S ONLY ABOUT 1500,000 ATOMS OF MERCURIED IN THE TUBE, 576 00:33:47,222 --> 00:33:49,073 WHICH IS A VERY SMALL AMOUNT OF MERCURY. 577 00:33:49,073 --> 00:33:51,242 IT'S VERY PRECISE WAY. 578 00:33:51,242 --> 00:33:53,478 IT TAKES MONTHS TO GET THE BALANCE JUST RIGHT IN THE 579 00:33:53,478 --> 00:33:59,434 MERCURY AS WE BUILD UP THE CLOCKS. 580 00:33:59,434 --> 00:34:03,988 SO TODD WAS TALKING ABOUT HOW IN THE DSN WE USE THE ATOMIC 581 00:34:03,988 --> 00:34:04,155 CLOCKS. 582 00:34:04,155 --> 00:34:08,259 YOU MAY HAVE HEARD RECENTLY THE NATIONAL INSTITUTE OF STANDARDS 583 00:34:08,259 --> 00:34:13,064 AND TECHNOLOGY, THEY'RE SORT OF THE UNITED STATES KEEPER OF 584 00:34:13,064 --> 00:34:13,214 TIME. 585 00:34:13,214 --> 00:34:18,069 THEY HAVE A CLOCK THE F 1. 586 00:34:18,069 --> 00:34:21,172 IT'S THE MOST ACCURATE CLOCK IN THE WORLD NOW. 587 00:34:21,172 --> 00:34:23,424 IT IS SORT OF LIKE WHO IS THE BEST QUARTERBACK? 588 00:34:23,424 --> 00:34:26,144 IT'S FLIPPING AROUND BETWEEN DIFFERENT ORGANIZATIONS. 589 00:34:26,144 --> 00:34:27,362 IT'S THE SIZE OF A KITCHEN. 590 00:34:27,362 --> 00:34:32,133 IT'S THE SIZE OF AN INDUSTRIAL KITCHEN. 591 00:34:32,133 --> 00:34:32,317 OKAY. 592 00:34:32,317 --> 00:34:34,202 IT IS QUITE ACCURATE. 593 00:34:34,202 --> 00:34:38,089 IT'S A DIFFERENT TECHNOLOGY THEY USE IT'S WHERE WE THROW THE 594 00:34:38,089 --> 00:34:40,358 ATOMS IN THE AIR AND THEY COME DOWN AND THEY'RE NOT CONNECTED 595 00:34:40,358 --> 00:34:45,246 TO ANYTHING AND THEY MEASURE THEM. 596 00:34:45,246 --> 00:34:51,152 OUR TECHNOLOGY HAS BEEN USED IN THE DSN AND IT STAND FOR LINEAR 597 00:34:51,152 --> 00:34:55,240 ION TRAP -- SOMETHING. 598 00:34:55,240 --> 00:34:57,408 IT'S ABOUT THE SIZE OF A REFRIGERATOR. 599 00:34:57,408 --> 00:34:59,193 IT'S A FANCY REFRIGERATOR. 600 00:34:59,193 --> 00:35:02,113 EACH ONE IS THE SIZE OF A REGULAR REFRIGERATOR. 601 00:35:02,113 --> 00:35:08,102 YOU GET THE IDEA FROM A KITCHEN TON A FRIDGE RATER TO ABOUT THE 602 00:35:08,102 --> 00:35:09,320 SIZE OF THE TOASTER OVEN. 603 00:35:09,320 --> 00:35:12,373 IT'S NOT ALL THAT HEAVY EITHER. 604 00:35:12,373 --> 00:35:14,175 THAT'S THE THING THE PROJECT HAS BEEN DOING. 605 00:35:14,175 --> 00:35:17,228 WE HAVE BEEN TAKING A TECHNOLOGY THAT HAS BEEN IN THE WORKS AND 606 00:35:17,228 --> 00:35:23,418 BEEN DEPLOYED FOR THE LAST FIVE TO TEN YEARS. 607 00:35:23,418 --> 00:35:26,404 IT'S BEEN IN THE WORKS EVEN LONGER. 608 00:35:26,404 --> 00:35:33,177 WE CAN SHRINK IT DOWN TO PUT IT ON A SPACECRAFT AND USE IT IN 609 00:35:33,177 --> 00:35:35,096 SPACE LIKE THE WAY TODD HAS BEEN TALKING ABOUT. 610 00:35:35,096 --> 00:35:38,449 IT'S A LITTLE DIFFERENT THAN THE NORMAL TYPE OF MISSION. 611 00:35:38,449 --> 00:35:42,086 OUR GOAL IS NOT TO GO AND GO TO A CERTAIN PLACE AND COLLECT 612 00:35:42,086 --> 00:35:45,240 SCIENCE ABOUT A CERTAIN TARGET, AS WE CALL IT. 613 00:35:45,240 --> 00:35:49,460 IT'S TO TEST THE CLOCK IN THE ENVIRONMENT OF SPACE AND ON A 614 00:35:49,460 --> 00:35:52,380 SPACECRAFT AND SEE HOW WELL IT WORKS. 615 00:35:52,380 --> 00:35:58,136 AND SEE WHERE THE WARTS ARE SO WE CAN DESIGN THE REAL ONE TO GO 616 00:35:58,136 --> 00:36:04,976 TO JUPITER OMR MARS. 617 00:36:04,976 --> 00:36:07,345 IT'S A NEW CLASS THAT NASA HAS BEEN DOING. 618 00:36:07,345 --> 00:36:09,030 WE'RE BUILDING THE PAYLOAD. 619 00:36:09,030 --> 00:36:09,447 THERE'S THE DLOK. 620 00:36:09,447 --> 00:36:13,334 THERE'S THE USO THAT TODD SHOWED YOU EARLIER. 621 00:36:13,334 --> 00:36:16,404 IT'S A MEASUREMENT DEVICE A GPS SIVER WE USE TO MEASURE THE 622 00:36:16,404 --> 00:36:17,305 CLOCK IN SPACE. 623 00:36:17,305 --> 00:36:20,258 WE PUT IT ON A SMALL SPACECRAFT. 624 00:36:20,258 --> 00:36:22,360 IT'S ABOUT THE SIZE OF THIS PODIUM. 625 00:36:22,360 --> 00:36:28,249 IT'S VERY SMALL COMPARED TO NORMAL JPL SPACECRAFT THAT WOULD 626 00:36:28,249 --> 00:36:29,434 REACH TO THE CEILING HERE. 627 00:36:29,434 --> 00:36:34,355 AND WE FLY THAT SPACECRAFT WITH A BUNCH OF OTHER SPACECRAFT ON A 628 00:36:34,355 --> 00:36:36,240 MISSION THAT THE AIR FORCE IS RUNNING. 629 00:36:36,240 --> 00:36:40,078 NOW WHEN I WAS A KID, I USED TO PLAY MONOPOLY WITH MY SISTERS. 630 00:36:40,078 --> 00:36:44,432 YOU SIT THERE AND YOU'VE GOT BALTIC AVENUE AND YOU WANT NORTH 631 00:36:44,432 --> 00:36:45,266 CAROLINA AVENUE. 632 00:36:45,266 --> 00:36:48,386 AND YOUR SISTER'S GOT IT SO YOU OFFER HERE, YOU KNOW, A 633 00:36:48,386 --> 00:36:52,390 RAILROAD, AND BALTIC, AND A LITTLE BIT OF CASH TO SWEETEN 634 00:36:52,390 --> 00:36:53,274 THE DEAL. 635 00:36:53,274 --> 00:36:55,159 MY OTHER SISTER WANTS IT, TOO. 636 00:36:55,159 --> 00:36:58,463 WE WORK OUT THE THREE WAY DEAL WHERE THERE'S THE MONEY AND 637 00:36:58,463 --> 00:37:00,415 PROPERTY CHANGING HAND. 638 00:37:00,415 --> 00:37:06,254 THAT'S THE WAY WE GET ON THE MISSIONS. 639 00:37:06,254 --> 00:37:09,323 WHAT HAPPENS IS A UNITED STATES SATELLITE PROVIDER HAS A MISSION 640 00:37:09,323 --> 00:37:12,360 WHERE THEY WANT TO FLY A LOT OF DEMONSTRATION PAYLOAD. 641 00:37:12,360 --> 00:37:17,982 WE'RE PAYING THEM FOR SEATS ON THEIR SPACECRAFT. 642 00:37:17,982 --> 00:37:20,318 IT'S LIKE PIEING AN AIRLINE TICKET. 643 00:37:20,318 --> 00:37:22,353 THEY'VE GOT OTHER PAYLOADS. 644 00:37:22,353 --> 00:37:25,256 AND THIS THEN WE'RE ALSO PAYING FOR TWO AIR FORCE PAYLOADS TO BE 645 00:37:25,256 --> 00:37:27,175 ON THIS SPACECRAFT. 646 00:37:27,175 --> 00:37:30,078 SO THE AIR FORCE WILL TURN AROUND AND GIVE US A RIDE ON 647 00:37:30,078 --> 00:37:30,378 THEIR ROCKET. 648 00:37:30,378 --> 00:37:34,248 WE START TRADING THINGS AROUND AND IT MAKES FOR AN INTERESTING 649 00:37:34,248 --> 00:37:36,200 AND COMPLEX ARRANGEMENT. 650 00:37:36,200 --> 00:37:39,103 IT SAVES THE TAXPAYERS A LOT OF MONEY. 651 00:37:39,103 --> 00:37:41,189 WE'RE NOT PAYING ANYTHING AT ALL FOR THE ROCKET. 652 00:37:41,189 --> 00:37:44,358 THE AIR FORCE IS FLYING THE ROCKET FOR ANOTHER REASON. 653 00:37:44,358 --> 00:37:47,211 ALL OF THE SATELLITES THAT ARE ON THE ROCKET ARE SORT OF 654 00:37:47,211 --> 00:37:49,180 GETTING A FREE RIDE. 655 00:37:49,180 --> 00:37:51,165 BECAUSE THE AIR FORCE WANTS TO CHECK IT OUT. 656 00:37:51,165 --> 00:37:53,317 IT'S A FALCON HEAVY, BY THE WAY. 657 00:37:53,317 --> 00:38:01,959 WHICH IS THE NEXT VERSION OF THE FALCON THAT IS SPACEX IS 658 00:38:01,959 --> 00:38:03,277 PLANNING TO FLY LATER THIS YEAR. 659 00:38:03,277 --> 00:38:06,330 IT'S BASICALLY THREE FALCON NINES TIED TOGETHER. 660 00:38:06,330 --> 00:38:07,965 IT'S A POWERFUL ROCKET. 661 00:38:07,965 --> 00:38:09,200 THE AIR FORCE WANTS TO CHECK IT OUT. 662 00:38:09,200 --> 00:38:13,387 WE GET TO RIDE PRETTY MUCH FOR FREE FOR CARRYING A COUPLE OF 663 00:38:13,387 --> 00:38:14,338 THEIR OTHER PAYLOAD. 664 00:38:14,338 --> 00:38:16,157 THAT'S HOW WE WORK THE DEALS OUT. 665 00:38:16,157 --> 00:38:18,126 I'M GOING TO HAND IT OVER TO TODD HERE. 666 00:38:18,126 --> 00:38:22,196 HE'S GOING TO SWITCH BACK NOW TO WHAT WE DO WITH THE CLOCK AND 667 00:38:22,196 --> 00:38:28,252 FANCY WAYS. >> THANKS. 668 00:38:28,252 --> 00:38:33,374 >> SO THE ROCKET PUTS US IN SPACE. 669 00:38:33,374 --> 00:38:42,083 IT'S A LOW-EARTH ORBIT IN WHICH ALLEN TALKED ABOUT. 670 00:38:42,083 --> 00:38:44,469 WE'LL SEE IF THAT'S THE DATE WE FLY. 671 00:38:44,469 --> 00:38:55,363 BUT ONCE WE ARE IN SPACE, SIRI NEEDS TO CHECK THE SPACECRAFT. 672 00:38:55,363 --> 00:38:59,100 AFTER A MONTH WE CHECK IT OUT AND SEE IF IT'S WORKING OKAY. 673 00:38:59,100 --> 00:39:02,053 WE'RE READY TO START THE NOMINAL MISSION. 674 00:39:02,053 --> 00:39:03,304 THAT'S ABOUT FIVE MONTHS LONG. 675 00:39:03,304 --> 00:39:06,340 THE WAY IN WHICH WE OPERATE THE MISSION IS THAT RECEIVER THAT 676 00:39:06,340 --> 00:39:12,146 ALLEN TALKED ABOUT IS GOING TO RECEIVE GPS SIGNALS FROM THE 677 00:39:12,146 --> 00:39:12,363 CONSTELLATION. 678 00:39:12,363 --> 00:39:16,300 SO THIS SPACECRAFT IS IN ABOUT A 700 KILOMETER ORBIT. 679 00:39:16,300 --> 00:39:20,071 THE GPS SATELLITES ARE ABOUT 20,000 KILOMETER ORBIT. 680 00:39:20,071 --> 00:39:22,089 WE SEE A LOT OF GPS SATELLITES. 681 00:39:22,089 --> 00:39:25,042 WE SEE ON AVERAGE ABOUT 12 CONTINUOUSLY. 682 00:39:25,042 --> 00:39:26,377 THAT'S A LOT OF DATA. 683 00:39:26,377 --> 00:39:28,362 AND IT'S FAIR TO ASK. 684 00:39:28,362 --> 00:39:29,013 OKAY. 685 00:39:29,013 --> 00:39:32,116 YOU'RE A NEW TYPE OF ATOMIC CLOCK. 686 00:39:32,116 --> 00:39:35,086 YOU SAID GPS HAS ATOMIC CLOCKS. 687 00:39:35,086 --> 00:39:36,170 IT'S SUPPOSED TO BE BETTER. 688 00:39:36,170 --> 00:39:37,405 HOW IS IT GOING TO WORK? 689 00:39:37,405 --> 00:39:44,345 IT TURNS OUT THERE ARE OVER 400 TRACKING STATIONS ON EARTH 690 00:39:44,345 --> 00:39:47,381 TRACKING THE GPS CONSTELLATION ALL THE TIME. 691 00:39:47,381 --> 00:39:51,118 AND THE TRACKING STATIONS HAVE DETERMINED THE LOCATION OF EACH 692 00:39:51,118 --> 00:39:53,321 SATELLITE CONTINUOUSLY TO ABOUT 2 CENTIMETERS. 693 00:39:53,321 --> 00:39:58,192 AND THE CLOCK ON BOARD TO ABOUT 50 -- EVEN THOUGH THE GPS CLOCK 694 00:39:58,192 --> 00:40:08,052 ISN'T AS STABLE AS OUR CLOCK, IT'S MOVING AROUND WE KNOW HOW. 695 00:40:08,052 --> 00:40:10,438 WE CAN DETERMINE HOW WELL THE CLOCK OPERATES. 696 00:40:10,438 --> 00:40:14,075 SO OUR REQUIREMENT IS TO SHOW THAT THE STABILITY IS BETTER 697 00:40:14,075 --> 00:40:16,177 THAN TWO NANO SECOND PER DAY. 698 00:40:16,177 --> 00:40:20,364 AND OUR GOAL IS ABOUT 3/10 OF A MECHANIC KNOW SECOND PER DAY. 699 00:40:20,364 --> 00:40:24,068 IF YOU REMEMBER WHEN I WAS TALKING ABOUT THE DSN, IT'S 700 00:40:24,068 --> 00:40:26,270 ABOUT A TENTH OF A MECHANIC KNOW SECOND PER DAY. 701 00:40:26,270 --> 00:40:30,224 WE'RE IN THE BALLPARK OF WHAT THE DSN IS ABLE TO PROVIDE. 702 00:40:30,224 --> 00:40:35,213 IN FACT, AT THESE LEVELS OTHER ERRORS IN THE DOPPLER 703 00:40:35,213 --> 00:40:38,416 MEASUREMENTS START TO DOMINATE THE MEASUREMENTS AND THE CLOCK 704 00:40:38,416 --> 00:40:40,484 AREA ESSENTIALLY GOES AWAY. 705 00:40:40,484 --> 00:40:46,257 WITH THAT WE'RE HOPING TO DEMONSTRATE THE UTILITIES FOR 706 00:40:46,257 --> 00:40:50,161 FUTURE MISSIONS TO SHOW IT CAN NAVIGATE THE TV QUITE WELL. 707 00:40:50,161 --> 00:40:56,500 AND THEN AFTER THAT FIRST FIVE MONTHS, WE'RE NOT A BIG MISSION 708 00:40:56,500 --> 00:41:02,039 AND WE'RE TRYING TO DO THIS AS EFFICIENTLY AND I DON'T WANT TO 709 00:41:02,039 --> 00:41:06,093 SAY CHEAPLY BUT, YOU KNOW, AS ECONOMICALLY AS WE CAN. 710 00:41:06,093 --> 00:41:12,300 SO WE'VE GOT THE DATA AND NOW WHAT WE'RE INTERESTED IN IS 711 00:41:12,300 --> 00:41:14,135 MAKING SURE THE THINGS STILL TICKS. 712 00:41:14,135 --> 00:41:17,505 FOR LONG LIFE DURATION MISSIONS, YOU NEED TO WORK FOR MORE THAN A 713 00:41:20,124 --> 00:41:18,155 YEAR. 714 00:41:20,124 --> 00:41:24,278 BUT WE CAN OPERATE LONGER AS LONG AS WE KEEP PAYING THE RENT 715 00:41:24,278 --> 00:41:27,131 ON THE SIRI SPACECRAFT. 716 00:41:27,131 --> 00:41:28,332 SO COOL STUFF. 717 00:41:28,332 --> 00:41:32,320 THIS IS OUR DEMONSTRATION CLOCK. 718 00:41:32,320 --> 00:41:34,038 IT'S A PROTOTYPE CLOCK. 719 00:41:34,038 --> 00:41:37,341 IT'S NOT THE FINAL CLOCK THAT WOULD GO ON A FUTURE MISSION. 720 00:41:37,341 --> 00:41:41,495 WHAT YOU WOULD DO NEXT IS -- WHAT WE'RE LEARNING AS PART OF 721 00:41:41,495 --> 00:41:47,435 OUR PROJECT HOW WE WOULD SHRINK IT FURTHER. 722 00:41:47,435 --> 00:41:53,240 WE'VE GOT LOTS OF IDEAS HOW TO CUT THAT BY A QUARTER AND MAKE 723 00:41:53,240 --> 00:41:54,392 IT ABOUT THIS BIG. 724 00:41:54,392 --> 00:41:57,295 IT'S VERY REASONABLE TO FLY ON FUTURE SPACE MISSIONS. 725 00:41:57,295 --> 00:42:03,034 SOME OF THE WAYS IN WHICH WE CAN USE IT FOR FUTURE MISSIONS IN 726 00:42:03,034 --> 00:42:06,203 THE ARENA OF SCIENCE AND NAVIGATION, LET'S TALK ABOUT 727 00:42:06,203 --> 00:42:07,371 THAT FOR A LITTLE BIT. 728 00:42:07,371 --> 00:42:12,093 HERE IS AN ILLUSTRATION OF TRANSMITTING A SIGNAL THROUGH 729 00:42:12,093 --> 00:42:14,478 THE RINGS AND RECEIVED HERE AT THE DSN. 730 00:42:14,478 --> 00:42:20,151 THIS IS THAT ONE WAY SIGNAL AGAIN AND THEY HAVE TO USE TODAY 731 00:42:20,151 --> 00:42:21,185 ARE USO. 732 00:42:21,185 --> 00:42:25,406 AND USOS ARE GREAT. 733 00:42:25,406 --> 00:42:29,243 YOU GET A LOT OF DATA TO PROBE THE RINGS BUT IT'S ABOUT TEN TO 734 00:42:29,243 --> 00:42:31,395 A HUNDRED TIMES MORE ACCURATE THAN THE MEASUREMENT. 735 00:42:31,395 --> 00:42:36,367 WE CAN LEARN A LOT MORE ABOUT THE RINGS IF IT WERE ON BOARD. 736 00:42:36,367 --> 00:42:40,454 PLACES LIKE MARS, SPACECRAFT TRANSMIT SIGNALS THROUGH THE 737 00:42:40,454 --> 00:42:45,192 ATMOSPHERE AS THE SATELLITE RISES AND SET, AND THAT SIGNAL 738 00:42:45,192 --> 00:42:47,044 GETS AFFECTED BY THE ATMOSPHERE. 739 00:42:47,044 --> 00:42:51,165 WE CAN LEARN A LOT ABOUT THE ATMOSPHERE BY MEASURING THESE 740 00:42:51,165 --> 00:42:51,332 SIGNALS. 741 00:42:51,332 --> 00:42:54,185 AGAIN, THIS IS A ONE WAY SIGNAL. 742 00:42:54,185 --> 00:42:59,390 SO MARS ORBITERS HAVE USO AND IT'S RECEIVED BACK HERE. 743 00:42:59,390 --> 00:43:02,159 AND THE USO IS THE LIMITING ERROR SOURCE. 744 00:43:02,159 --> 00:43:06,464 IF IT WERE ON BOARD, IT WOULD BE TEN TO A HUNDRED TIMES MORE 745 00:43:06,464 --> 00:43:07,148 ACCURATE. 746 00:43:07,148 --> 00:43:13,287 OTHER WAYS IN WHICH WE CAN USE IT IS PUT IT ON BOARD THE 747 00:43:13,287 --> 00:43:16,407 ORBITER TO RECALL THAT ILLUSTRATION I HAD EARLIER WHERE 748 00:43:16,407 --> 00:43:19,443 THE SATELLITES WERE GETTING A LOT OF DATA. 749 00:43:19,443 --> 00:43:21,278 ALMOST CONTINUOUSLY. 750 00:43:21,278 --> 00:43:26,467 QUESTION TAKE ADVANTAGE OF THAT OR AN ORBIT AROUND MARS AND 751 00:43:26,467 --> 00:43:33,374 USING IT WITH THE DATA AND USING THE FACT THAT WE CAN DIAL INTO 752 00:43:33,374 --> 00:43:34,075 THE KSN AT. 753 00:43:34,075 --> 00:43:38,095 TODAY WE USE X BAN. 754 00:43:38,095 --> 00:43:40,481 IT'S ABOUT 40 GIG HERTZ. 755 00:43:40,481 --> 00:43:44,518 THE DATA WE GET IS TEN TIMES MORE ACCURATE THAN THE X BAND. 756 00:43:44,518 --> 00:43:48,189 IT YOU DOUBLE THE DATA AND IMPROVE DATA, WE CAN DETERMINE 757 00:43:48,189 --> 00:43:50,074 THINGS LIKE THE GRAVITY FIELD. 758 00:43:50,074 --> 00:43:53,377 THE LONG-TERM GRAVITY FIELD AT MARRS VERY ACCURATELY. 759 00:43:53,377 --> 00:43:59,083 ONE OF THE THINGS THAT WE LEARN RECENTLY IS THAT THERE'S A LOT 760 00:43:59,083 --> 00:44:05,439 OF ICE MASS REDISTRIBUTION OVER THE COURSE OF A YEAR. 761 00:44:05,439 --> 00:44:09,443 THEY MIGHT BE ABLE TO CONTRIBUTE TO UNDERSTANDING THAT BETTER. 762 00:44:09,443 --> 00:44:15,399 OTHER WAYS IN WHICH WE CAN USE IT IS NASA IS DEVELOPING A 763 00:44:15,399 --> 00:44:21,439 SPACECRAFT TO EXPLORE YOU ROW PA. 764 00:44:21,439 --> 00:44:23,107 A MOON OF JUPITER. 765 00:44:23,107 --> 00:44:24,492 IT'S ENCASED IN AN ICE SHELL. 766 00:44:24,492 --> 00:44:29,196 ALL THE DATA SAID THERE'S AN OCEAN UNDERNEATH THAT ICE. 767 00:44:29,196 --> 00:44:35,186 ONE OF THE KEY THINGS THAT THE MISSION WILL DO IS PROBE THE 768 00:44:35,186 --> 00:44:38,339 CHARACTERS OF THE ICE AND THE OCEAN UNDERNEATH USING A VARIETY 769 00:44:38,339 --> 00:44:39,340 OF INSTRUMENTS. 770 00:44:39,340 --> 00:44:43,194 AND ONE OF THOSE INVESTIGATIONS IS GOING TO INVOLVE DETERMINING 771 00:44:43,194 --> 00:44:46,030 THE GRAVITY FIELD AROUND IT. 772 00:44:46,030 --> 00:44:50,134 AND MUCH LIKE BEFORE, THIS EXAMPLE WE'RE PROBING THE 773 00:44:50,134 --> 00:44:51,252 GRAVITY FIELD HERE. 774 00:44:51,252 --> 00:44:57,458 WE'RE PROBING THE GRAVITY FIELD OF UROPA AND THROUGH THAT WE CAN 775 00:44:57,458 --> 00:45:01,195 DETECT AND CONFIRM THE OCEAN UNDERNEATH THE ICE. 776 00:45:01,195 --> 00:45:06,317 UNFORTUNATELY, TO GET THAT DATA WE EITHER HAVE TO POINT THE HIGH 777 00:45:06,317 --> 00:45:13,991 GAIN ANTENNA AT EARTH, OR DEPLOY MEDIUM ANTENNAS ON THIS AND 778 00:45:13,991 --> 00:45:16,160 OTHER FACETS OF THE SPACECRAFT AND POINT THE VEHICLE TO EARTH 779 00:45:16,160 --> 00:45:17,077 TO GET IT. 780 00:45:17,077 --> 00:45:21,332 AND WHAT IT MEANS IS ALL THE INSTRUMENTS THAT ARE ORIENTED 781 00:45:21,332 --> 00:45:26,103 TOWARD UROPA GET POINTED AWAY. 782 00:45:26,103 --> 00:45:26,370 THAT'S NOT GOOD. 783 00:45:26,370 --> 00:45:29,423 WE CAN TAKE ADVANTAGE OF THE FACT THAT ON BOARD EVERY 784 00:45:29,423 --> 00:45:32,443 SPACECRAFT ARE THE LITTLE ANTENNA. 785 00:45:32,443 --> 00:45:40,217 WHAT IS NIFTY THEY HAVE A LARGE VIEW OF SPACE AROUND THEM. 786 00:45:40,217 --> 00:45:43,270 THESE ANTENNA HAVE A VERY NARROW VIEW. 787 00:45:43,270 --> 00:45:47,341 WE TAKE THE LOW GAIN ANTENNA AND YOU REMEMBER THE ANTENNA THAT 788 00:45:47,341 --> 00:45:50,027 WAS BIG WITH ALL THE POWER TRANSMITTING? 789 00:45:50,027 --> 00:45:54,164 WE CAN ACTUALLY TRACK THOSE SIGNALS WITH LOW GAIN ANTENNA ON 790 00:45:54,164 --> 00:45:56,166 BOARD A VEHICLE. 791 00:45:56,166 --> 00:46:00,971 IF YOU ADD IT TO THAT MIX, NOW THAT DATA WE'RE COLLECTING IS 792 00:46:00,971 --> 00:46:01,171 ACCURATE. 793 00:46:01,171 --> 00:46:03,290 ACCURATE ENOUGH TO DETERMINE THE GRAVITY FIELD. 794 00:46:03,290 --> 00:46:08,112 IF WE WERE TO BE ON BOARD THE VEHICLE, WE WOULD DELIVER ABOUT 795 00:46:08,112 --> 00:46:12,416 THREE TIMES MORE DATA THAN WE WOULD GET VERSUS USING THE THIS 796 00:46:12,416 --> 00:46:13,100 ANTENNA. 797 00:46:13,100 --> 00:46:17,054 OTHER MISSIONS THAT NASA IS CONTEMPLATING IS SENDING 798 00:46:17,054 --> 00:46:17,471 BALLOONS TO TIE TAN. 799 00:46:17,471 --> 00:46:22,059 TIE TAN HAS AN ATMOSPHERE OF NITROGEN. 800 00:46:22,059 --> 00:46:24,295 WE SPECULATE THERE ARE SEAS OF METHANE. 801 00:46:24,295 --> 00:46:28,399 IT'S A VERY OCEANY WORLD, AND ONE OF THE WAYS IN WHICH WE CAN 802 00:46:28,399 --> 00:46:31,368 EXPLORE THE SET OF BALLOONS TO FLOAT IN THE ATMOSPHERE AND LET 803 00:46:31,368 --> 00:46:33,420 IT DRIFT. 804 00:46:33,420 --> 00:46:37,141 BUT ONE OF THE THINGS THAT WOULD BE DIFFICULT IS TO TRACK WHERE 805 00:46:37,141 --> 00:46:44,431 THE BALLOON IS AT AS IT'S COURSING OVERTY TAN. 806 00:46:44,431 --> 00:46:48,252 IF YOU HAD A SMALL VERSION AND TAKE ADVANTAGE OF THE HIGH POWER 807 00:46:48,252 --> 00:46:49,486 TRANSMITTING TO THE VEHICLE. 808 00:46:49,486 --> 00:46:57,094 YOU PROBABLY HAVE FOUR 30-METERS ANTENNA TO GET ENOUGH POWER. 809 00:46:57,094 --> 00:47:00,381 YOU CAN TRACK THE BALLOON AND CHART THE COURSE. 810 00:47:00,381 --> 00:47:04,335 YOU CAN CORRELATE THE COURSE WITH THE SCIENCE DATA THE 811 00:47:04,335 --> 00:47:07,171 BALLOON IS COLLECTING AND TRANSMITTING BACK TO EARTH. 812 00:47:07,171 --> 00:47:10,057 SO THOSE ARE NIFTY SCIENCE APPLICATIONS. 813 00:47:10,057 --> 00:47:11,158 LET'S GET BACK TO NAVIGATION. 814 00:47:11,158 --> 00:47:13,978 AND I'M GOING TO LOOK AT MARS. 815 00:47:13,978 --> 00:47:17,264 ONE OF THE NEXT MISSIONS THAT WE'RE ENVISIONING GOING TO MARS 816 00:47:17,264 --> 00:47:21,118 IS AN ORBITER IN 2022. 817 00:47:21,118 --> 00:47:26,240 AND ONE OF THE WAYS IN WHICH WE'RE HOPING OR PLANNING NOW IS 818 00:47:26,240 --> 00:47:32,446 TO INSERT INTO THE LOW ORBIT USING SOLAR ELECTORATE 819 00:47:32,446 --> 00:47:33,163 PROPULSION. 820 00:47:33,163 --> 00:47:38,469 IT IMPARTS A SMALL ACCELERATION AND THE SPACECRAFT WILL SLOWLY 821 00:47:38,469 --> 00:47:40,421 SPIRAL INTO THE ORBIT. 822 00:47:40,421 --> 00:47:43,107 NAVIGATION WISE IT'S A PRETTY INTENSE PERIOD OF TIME. 823 00:47:43,107 --> 00:47:44,308 IT TAKES A LONG TIME. 824 00:47:44,308 --> 00:47:47,394 IF YOU HAD D SACK ON BOARD, YOU COULD TAKE ADVANTAGE OF THE 825 00:47:47,394 --> 00:47:53,267 ABILITY TO GET THE DATA WITHOUT IMPACTING OTHER MISSIONS THAT 826 00:47:53,267 --> 00:47:54,418 MEET THE DATA AT THE SAME TIME. 827 00:47:54,418 --> 00:47:59,306 YOU CAN COLLECT IT AND PROCESS IT AND IMPROVE OUR ABILITY TO DO 828 00:47:59,306 --> 00:47:59,506 NAVIGATION. 829 00:47:59,506 --> 00:48:06,130 ANOTHER WAY IN WHICH IT COULD BE HELPFUL IS THINKING FORWARD TO 830 00:48:06,130 --> 00:48:07,414 HUMANS GOING TO MARS. 831 00:48:07,414 --> 00:48:11,251 THERE'S GOING TO BE PROBABLY VEHICLES GOING TO MARS. 832 00:48:11,251 --> 00:48:18,409 IF YOU HAD IT ON BOARD, ON TRANSMISSIONS ON THE SPACECRAFT 833 00:48:18,409 --> 00:48:22,229 AND COUPLE IT WITH ON BOARD COMPUTERS YOU CAN COMPUTE THE 834 00:48:22,229 --> 00:48:27,267 TRAJECTORY IN REAL TIME THAT ASTRONAUTS TO USE TO SAFELY AND 835 00:48:27,267 --> 00:48:33,323 ROBUSTLY MAKE THEIR WAY TO MARS. 836 00:48:33,323 --> 00:48:34,341 EITHER AN ORBIT OR LAND. 837 00:48:34,341 --> 00:48:36,477 THOSE ARE SO. APPLICATIONS WE'RE ENVISIONINGS. 838 00:48:36,477 --> 00:48:38,379 I HOPE YOU LIKED OUR TALK TODAY. 839 00:48:38,379 --> 00:48:42,266 I THOUGHT I WOULD END WITH A FEW PICTURES HERE ILLUSTRATING 840 00:48:42,266 --> 00:48:47,354 CLOCKS OVER THE PAST QUARTER MILLENNIUM. 841 00:48:47,354 --> 00:48:50,257 AND NUMBERICALLY IMPROVING STABILITY. 842 00:48:50,257 --> 00:48:56,030 THERE'S HARRISON'S WATCH AT A TENTH OF A SECOND PER DAY. 843 00:48:56,030 --> 00:49:00,300 AND THEM CAME ALONG USO IN THE 1960s AND THEY'RE 2,000 TIMES 844 00:49:00,300 --> 00:49:04,955 MORE STABLE AT THE MICROSECOND PER DAY. 845 00:49:04,955 --> 00:49:13,363 NOW WE HAVE THIS AT ABOUT 3/10 OF A NANO SECOND PER DAY. 846 00:49:13,363 --> 00:49:20,070 WE'RE HAPPY TO ANSWER ANY QUESTIONS YOU MIGHT HAVE. 847 00:49:20,070 --> 00:49:29,413 [ APPLAUSE ] IF ANYBODY HAS ANY QUESTIONS, 848 00:49:29,413 --> 00:49:33,367 COME DOWN TO THE MIKES. 849 00:49:33,367 --> 00:49:37,221 WE DID A GOOD JOB OF EXPLAINING EVERYTHING. 850 00:49:37,221 --> 00:49:43,060 >> CRYSTAL CLEAR. >> DON'T BE SHY. 851 00:49:43,060 --> 00:49:43,277 HERE'S ONE. 852 00:49:43,277 --> 00:49:44,378 >> I HAVE A QUESTION. 853 00:49:44,378 --> 00:49:48,415 SO THE MOST ACCURATE CLOCK IN THE WHOLE WORLD. 854 00:49:48,415 --> 00:49:53,187 YOU SAID A LITTLE BIT ABOUT HOW YOU CAN TRY TO MEASURE THE 855 00:49:53,187 --> 00:49:58,041 ACCURACY OF VERY ACCURATE CLOCKS USING THIS CONSTELLATION OF GPS 856 00:49:58,041 --> 00:49:58,242 SATELLITES. 857 00:49:58,242 --> 00:50:04,481 HOW IS THE ERROR IN THE MOST ACCURATE CLOCK IN THE WORLD 858 00:50:04,481 --> 00:50:07,367 MEASURED? 859 00:50:07,367 --> 00:50:08,185 >> YEAH. 860 00:50:08,185 --> 00:50:11,138 IT'S MORE ACCURATE THAN ANY OTHER CLOCK. 861 00:50:11,138 --> 00:50:15,509 IT'S NOT MORE ACCURATE THAN A BUNCH OF CLOCKS TOGETHER. 862 00:50:15,509 --> 00:50:20,164 SO MATHEMATICALLY YOU CAN COMBINE THE ACCURACY OF AN 863 00:50:20,164 --> 00:50:23,050 ENSEMBLE OF CLOCKS AND COMPARE IT AGAINST THAT. 864 00:50:23,050 --> 00:50:44,238 IT'S SIMILAR TO WHAT WE'RE DOING WITH THE ECHO IN ORBIT. 865 00:50:44,238 --> 00:50:52,396 [ INAUDIBLE ] >> I'LL LET ALLEN ANSWER THAT 866 00:50:52,396 --> 00:50:56,116 ONE. >> I'M SORRY. 867 00:50:56,116 --> 00:50:57,317 WHAT WAS THAT? 868 00:50:57,317 --> 00:50:59,319 >> WHAT'S THE LIFETIME OF THE CLOCK? 869 00:50:59,319 --> 00:51:02,089 HOW DO YOU KNOW IT'S GOING TO WORK FOR MANY YEARS? 870 00:51:02,089 --> 00:51:08,412 >> THE LIMITATION FOR MOST SPACE FARING EQUIPMENT ARE THE 871 00:51:08,412 --> 00:51:12,165 ELECTRONICS AND THE FACT THAT IT'S ALTERNATELY EITHER VERY 872 00:51:12,165 --> 00:51:15,335 COLD AND HOT OR JUST VERY COLD ALL THE TIME OR AS THE 873 00:51:15,335 --> 00:51:18,222 SPACECRAFT HEATS UP IT GETS COLD AND THEN HOT. 874 00:51:18,222 --> 00:51:21,441 THAT MAKES ALL THE ELECTRONIC BOARDS, SAME WAY THAT 875 00:51:21,441 --> 00:51:23,243 ELECTRONICS IN YOUR CAR GO OUT. 876 00:51:23,243 --> 00:51:26,463 THEY EXPAND AND CONTRACT AND EVENTUALLY SOMETHING BREAKS. 877 00:51:26,463 --> 00:51:32,369 SO THAT'S THE FUNDAMENTAL LIMIT TO THE LIFETIME OF THE CLOCK. 878 00:51:32,369 --> 00:51:36,523 WE HAVE TUBES, LIKE THE LITTLE ION TRACK TUBES. 879 00:51:36,523 --> 00:51:37,324 THEY'RE SEALED. 880 00:51:37,324 --> 00:51:40,410 SOME HAVE LASTED WELL OVER FIVE YEARS. 881 00:51:40,410 --> 00:51:42,446 GOSH, I GUESS IT'S NINE YEARS NOW. 882 00:51:42,446 --> 00:51:44,448 IT WAS FIVE WHEN WE STARTED THIS PROJECT. 883 00:51:44,448 --> 00:51:51,288 SO WE DON'T SEE -- WE CAN MAKE A SEAL THAT LASTS A LONG, LONG 884 00:51:51,288 --> 00:51:51,538 TIME. 885 00:51:51,538 --> 00:51:55,242 THE MERCURY ATOMS AND THE THINGS INSIDE OF THE TUBES DON'T 886 00:51:55,242 --> 00:51:56,193 ACTUALLY GO AWAY. 887 00:51:56,193 --> 00:52:00,097 SO IT'S REALLY JUST THE ELECTRONICS. 888 00:52:00,097 --> 00:52:01,999 >> OKAY. 889 00:52:01,999 --> 00:52:06,370 SO MY QUESTION, THE ONE-WAY TRACKING THAT YOU CAN DO WITH 890 00:52:06,370 --> 00:52:17,064 THE ACCURATE ATOMIC CLOCK, YOU -- YOU'RE ONLY GETTING RADIO 891 00:52:17,064 --> 00:52:17,281 INFORMATION. 892 00:52:17,281 --> 00:52:22,052 YOU'RE ONLY GETTING VERY ACCURATE -- 893 00:52:22,052 --> 00:52:29,426 >> INSIDE INFORMATION. >> WOULD -- AT SOME POINT IN THE 894 00:52:29,426 --> 00:52:34,431 FUTURE, COULD YOU HAVE A SECOND MASTER STATION THAT MAY BE 895 00:52:34,431 --> 00:52:37,351 MONITORED OR SOMETHING AND THEN YOU COULD GET, RANGING FROM TWO 896 00:52:37,351 --> 00:52:38,151 DIFFERENT DIRECTIONS? 897 00:52:38,151 --> 00:52:41,171 >> YOU COULD. >> WOULDN'T THAT BE BETTER? 898 00:52:41,171 --> 00:52:46,226 >> ONE OF THE CONCEPTS FOR HUMANS GOING TO MARS IS TO PUT A 899 00:52:46,226 --> 00:52:48,178 MARS AREA STATIONARY SATELLITE. 900 00:52:48,178 --> 00:52:53,367 THAT WOULD PROVIDE TRACKING SERVICES WHILE AT MARS FOR THE 901 00:52:53,367 --> 00:52:55,452 ASTRONAUTS ON THE SURFACE AS WELL AS APPROACHING VEHICLES. 902 00:52:55,452 --> 00:52:59,172 IN THE LITTLE CARTOON I SHOWED, ACTUALLY TWO ARROWS GOING TO THE 903 00:52:59,172 --> 00:53:00,090 LITTLE ROCKET. 904 00:53:00,090 --> 00:53:03,176 THAT WAS DEMONSTRATING THAT VERY POSSIBILITY. 905 00:53:03,176 --> 00:53:08,365 ANOTHER THING, WHICH WE HAVE ACTUALLY DONE QUITE A BIT OF. 906 00:53:08,365 --> 00:53:13,153 JPL IS FAMOUS FOR DOING OPTICAL NAVIGATION. 907 00:53:13,153 --> 00:53:18,008 WE TAKE IMAGES OF SLES TEAL BODIES WITH A STAR BURST 908 00:53:18,008 --> 00:53:18,208 BACKGROUND. 909 00:53:18,208 --> 00:53:23,180 AND YOU CAN FIND YOUR LOCATION RELATIVE TO THE BODIES AND 910 00:53:23,180 --> 00:53:26,099 COUPLE THAT PROCESS. 911 00:53:26,099 --> 00:53:28,502 IT'S LINE OF SIGHT INFORMATION THAT THE RANGING PROVIDES. 912 00:53:28,502 --> 00:53:32,422 NOW YOU HAVE A MORE COMPLETE KIND OF THREE DIMENSIONAL FIX OF 913 00:53:32,422 --> 00:53:34,174 YOUR LOCATION IN SPACE. 914 00:53:34,174 --> 00:53:38,228 SO THAT'S ANOTHER POSSIBILITY THAT WE COULD -- THAT WE'RE 915 00:53:38,228 --> 00:53:39,279 ENVISIONING. >> THANK YOU. 916 00:53:39,279 --> 00:53:40,113 >> OKAY. 917 00:53:40,113 --> 00:53:43,316 WE HAVE SOME -- I GUESS THESE ARE SOCIAL MEDIA QUESTIONS. 918 00:53:43,316 --> 00:53:49,056 I HAVE BEEN HANDED. >> SO THE FIRST ONE IS, IS FOR 919 00:53:49,056 --> 00:53:49,406 TODD. >> OKAY. 920 00:53:49,406 --> 00:53:55,128 >> WHAT ARE THE EFFECTS OF GENERAL RELATIVITY ON ATOMIC 921 00:53:55,128 --> 00:53:57,447 CLOCKS IN OUTER SPACE FOR FROM EARTH'S GRAVITATIONAL FIELD? 922 00:53:57,447 --> 00:54:01,268 >> SO THE GPS SYSTEM ACTUALLY HAS TO DEAL WITH THIS. 923 00:54:01,268 --> 00:54:05,222 THEY ACTUALLY -- THE FREQUENCY THAT IT WOULD NATURALLY TRANSMIT 924 00:54:05,222 --> 00:54:09,009 IN ITS ORBIT, THEY ACTUALLY ARTIFICIALLY REDUCE THAT 925 00:54:09,009 --> 00:54:13,130 FREQUENCY BECAUSE THE CLOCKS ON EARTH TICK AT A DIFFERENT RATE 926 00:54:13,130 --> 00:54:16,166 THAN THE CLOCKS IN THE GPS CONSTELLATION. 927 00:54:16,166 --> 00:54:18,201 SO THIS IS A FACT OF LIFE. 928 00:54:18,201 --> 00:54:19,453 THIS IS SOMETHING WE HAVE TO DEAL WITH. 929 00:54:19,453 --> 00:54:23,473 WE HAVE TO DEAL WITH IT TODAY REPEATEDLY, EVEN WITH TWO-WAY 930 00:54:23,473 --> 00:54:24,241 DATA. 931 00:54:24,241 --> 00:54:30,213 USING DSAC IN THE FUTURE WITH ONE-WAY DATA WE'D HAVE TO 932 00:54:30,213 --> 00:54:32,232 CORRECT FOR CERTAIN EFFECTS. 933 00:54:32,232 --> 00:54:34,434 THEY'RE SMALL BUT SUBSTANTIAL. 934 00:54:34,434 --> 00:54:38,138 IF WE DIDN'T CORRECT FOR THEM THEY WOULD BE THE LARGEST ERROR 935 00:54:38,138 --> 00:54:45,128 SOURCE THAT WE'D ENCOUNTER IN GOING TO PLACES LIKE MARS AND 936 00:54:45,128 --> 00:54:48,181 JUPITER. >> DO THEY CLICK FASTER OR 937 00:54:48,181 --> 00:54:51,501 SLOWER AT MARS. >> THEY CLICK FASTER. 938 00:54:51,501 --> 00:54:54,421 >> WE SPENT AN HOUR THIS AFTERNOON TRYING TO FIGURE OUT 939 00:54:54,421 --> 00:55:01,144 THE ANSWER TO THAT QUESTION IN CASE SOMEBODY ANSWERED IT. 940 00:55:01,144 --> 00:55:02,262 >> IF YOU DON'T GET IT RIGHT, YOU GET IT WRONG. 941 00:55:02,262 --> 00:55:04,314 >> I HAVE ANOTHER QUESTION. 942 00:55:04,314 --> 00:55:07,167 DSAC OPERATES AT THE LEVEL OF ATOMS. 943 00:55:07,167 --> 00:55:12,022 ARE THERE ANY CHALLENGES BECAUSE OF QUANTUM MECHANICS? 944 00:55:12,022 --> 00:55:14,991 ACTUALLY, WE USE QUANTUM MECHANICAL EFFECTS. 945 00:55:14,991 --> 00:55:21,081 THAT'S EXACTLY HOW THIS I WAS TALKING ABOUT WITH THIS ELECTRON 946 00:55:21,081 --> 00:55:23,116 IS A QUANTUM MECHANIC EFFECT. 947 00:55:23,116 --> 00:55:28,338 ONE OF OF THE REASON WE TRAP THE IONS IN A FIELD IS REDUCE 948 00:55:28,338 --> 00:55:31,024 PROHIATIONS ON THE ATOMS. 949 00:55:31,024 --> 00:55:36,246 WE DON'T GET TO THE LEVEL OF QUANTUM MECHANICAL EFFECTS IN 950 00:55:36,246 --> 00:55:36,396 THAT. 951 00:55:36,396 --> 00:55:40,400 SO THE CHALLENGES ARE TO DESIGN A VERY MAGNETICALLY CLEAN CLOCK. 952 00:55:40,400 --> 00:55:42,436 THAT WHOLE CLOCK, ALL THAT METAL. 953 00:55:42,436 --> 00:55:44,237 NONE OF IT IS MAGNETIC. 954 00:55:44,237 --> 00:55:47,140 IT'S ALL NON-MAGNETIC METALS. 955 00:55:47,140 --> 00:55:52,145 THE MAGNETIC FIELDS, THE STRAY MAGNETIC FIELDS WOULD INDUCE A 956 00:55:52,145 --> 00:55:53,430 QUANTUM MECHANICAL EFFECT. 957 00:55:53,430 --> 00:55:57,317 THAT'S A CHALLENGE BECAUSE NON-MAGNETIC SCREWS ARE HARD TO 958 00:55:57,317 --> 00:56:00,170 FIND. >> TO FOLLOW UP ON THAT, WE TALK 959 00:56:00,170 --> 00:56:03,123 ABOUT THE HARSH ENVIRONMENT OF SPACE AND PEOPLE'S PERCEPTIONS 960 00:56:03,123 --> 00:56:05,258 MIGHT BE THE SPACE AROUND THE VEHICLE. 961 00:56:05,258 --> 00:56:08,411 BUT REALLY THE SPACE INSIDE THE VEHICLE IS AN ENVIRONMENT WE 962 00:56:08,411 --> 00:56:11,998 HAVE TO DEAL WITH, THE CHANGING TEMPERATURES INSIDE THE 963 00:56:11,998 --> 00:56:17,454 SPACECRAFT, THE MAGNETIC FIELDS FROM THE OUTER ENVIRONMENT AS 964 00:56:17,454 --> 00:56:23,160 WELL AS FROM THE SPACE FIELD ITSELF COULD IMPACT THE CLOCK. 965 00:56:23,160 --> 00:56:24,361 >> ANOTHER QUESTION. 966 00:56:24,361 --> 00:56:30,400 COULD NEARBY SPACECRAFT USE A DSAC THAT IS CLOSE BY? 967 00:56:30,400 --> 00:56:36,106 >> SO, WHAT DSAC DOES, WE DIDN'T REALLY GET INTO THIS -- IT TAKES 968 00:56:36,106 --> 00:56:41,211 A USO AND USES THE TUNING FORK FEATURE, AND WE CONTROL THE 969 00:56:41,211 --> 00:56:45,332 OUTPUT OF THE USO TO GET A MORE STABLE FREQUENCY ON LONGER TIME 970 00:56:45,332 --> 00:56:46,032 SCALES. 971 00:56:46,032 --> 00:56:50,020 IN TEN SECONDS WE'RE REALLY ADOPTING THE STABILITY OF THE 972 00:56:50,020 --> 00:56:52,272 USO THAT IS PART OF THIS PROCESS. 973 00:56:52,272 --> 00:56:57,510 AND IN FACT, USOs ARE USED ROUTINELY FOR COMMUNICATING 974 00:56:57,510 --> 00:56:59,129 BETWEEN NEARBY SPACECRAFT. 975 00:56:59,129 --> 00:57:04,034 AN EXAMPLE THAT WE USE, EARTH AND AT THE MOON, EARTH IS THE 976 00:57:04,034 --> 00:57:05,368 GRACE MISSION. 977 00:57:05,368 --> 00:57:09,089 THEY USE COMMUNICATION LINKS BETWEEN TWO SPACECRAFT THAT ARE 978 00:57:09,089 --> 00:57:13,009 IN ORBIT. 979 00:57:13,009 --> 00:57:17,414 THEY'RE A FEW HUNDRED KILOMETERS APART AND THE TIME FOR THE 980 00:57:17,414 --> 00:57:22,435 SIGNAL TO GO BACK AND FORTH IS VERY SHORT. 981 00:57:22,435 --> 00:57:26,339 WHAT MATTERS FOR DSAC IS LOOKING AT THE EVOLUTION OF THE 982 00:57:26,339 --> 00:57:29,442 FREQUENCY IN TIME OVER LONG PERIODS OF TIME. 983 00:57:29,442 --> 00:57:33,296 YOU'RE TAKING MEASUREMENTS AT A PERIOD OF TIME, AND THEN YOU'RE 984 00:57:33,296 --> 00:57:36,333 NOT TAKING MEASUREMENTS FOR A DAY, AND YOU START TAKING THEM 985 00:57:36,333 --> 00:57:37,000 AGAIN. 986 00:57:37,000 --> 00:57:40,053 YOU DON'T WANT YOUR FREQUENCY AND TIME SOURCE TO HAVE DRIFTED 987 00:57:40,053 --> 00:57:42,122 SIGNIFICANTLY AWAY FROM WHAT IT'S SUPPOSED TO BE. 988 00:57:42,122 --> 00:57:45,475 THAT BECOMES AN ERROR THAT YOU HAVE TO DEAL WITH IN THE 989 00:57:45,475 --> 00:57:46,493 TRAJECTORY DETERMINATION PROCESS. 990 00:57:46,493 --> 00:57:50,380 REMEMBER, WE HAVE ONLY A LIMITED AMOUNT OF DATA TO FIGURE OUT THE 991 00:57:50,380 --> 00:57:51,398 TRAJECTORY. 992 00:57:51,398 --> 00:57:53,216 ERRORS LIKE CLOCKS MAKE THAT HARDER. 993 00:57:53,216 --> 00:57:53,383 >> OKAY. 994 00:57:53,383 --> 00:57:56,469 THIS ONE IS FROM AN USTREAM CHAT. 995 00:57:56,469 --> 00:57:58,071 WE GOT YOU COVERED. 996 00:57:58,071 --> 00:58:03,209 COULDEN A EARTH ORBITING DSAC AUGMENT THE DEEP SPACE NETWORK 997 00:58:03,209 --> 00:58:06,446 FOR NAVIGATING EXISTING PROBES AND MISSIONS? 998 00:58:06,446 --> 00:58:09,449 >> THE CHALLENGE THERE IS, YOU KNOW, ONE ANSWER WOULD BE YES. 999 00:58:09,449 --> 00:58:14,187 BUT ACTUALLY THE REAL CHALLENGE FOR AN ORBITING SPACECRAFT IS 1000 00:58:14,187 --> 00:58:16,156 KNOWING ITS LOCATION PRECISELY. 1001 00:58:16,156 --> 00:58:23,213 SO, FOR THIS DSM ENTERPRISE TO WORK, WE ACTUALLY DO LOCATION OF 1002 00:58:23,213 --> 00:58:36,476 THE -- OF MONUMENTS THAT DEFINE THE CENTER TO WITHIN A 1003 00:58:36,476 --> 00:58:40,413 CENTIMETER OF WHERE THAT WILL IT WILL THE ANTENNA. 1004 00:58:40,413 --> 00:58:45,201 WE WOULD BE CHALLENGED FOR A SPACECRAFT TO HAVE THAT KIND OF 1005 00:58:45,201 --> 00:58:45,402 ACCURACY. 1006 00:58:45,402 --> 00:58:48,088 WHILE THE FREQUENCY AND TIME STABILITY ON THE SATELLITE WOULD 1007 00:58:48,088 --> 00:58:51,391 BE GOOD AND COULD AUGMENT THE DSN. 1008 00:58:51,391 --> 00:58:56,212 WE WOULD BE CHALLENGED KNOWING WHERE THE SPACECRAFT IS AT TO 1009 00:58:56,212 --> 00:59:03,286 PARTICIPATE IN THIS NAVIGATION ENTERPRISE. 1010 00:59:03,286 --> 00:59:08,224 >> FROM THE SOUND OF THINGS, THERE IS KIND OF A LOG JAM OR A 1011 00:59:08,224 --> 00:59:11,277 TRAFFIC JAM, BOTTLE NECK, AT THE DEEP SPACE NETWORK. 1012 00:59:11,277 --> 00:59:18,268 CAN YOU COMMENT ABOUT ANY PLANS TO EXPAND THE DSN TO -- BECAUSE, 1013 00:59:18,268 --> 00:59:21,254 UNLESS THE CURRENT MISSIONS ARE BASICALLY GOING TO DIE OUT IN 1014 00:59:21,254 --> 00:59:26,159 THE NEXT FEW YEARS, WITH THE NUMBER OF MISSIONS THAT WILL BE 1015 00:59:26,159 --> 00:59:32,248 COMING ONLINE, WE'RE GOING TO BE NEEDING MORE DSN CAPABILITY. 1016 00:59:32,248 --> 00:59:35,218 >> THERE ARE CURRENTLY FIVE MISSIONS AT MARS RIGHT NOW, 1017 00:59:35,218 --> 00:59:36,302 RIGHT? 1018 00:59:36,302 --> 00:59:37,270 IS IT FIVE? 1019 00:59:37,270 --> 00:59:44,361 >> FIVE -- YEAH. >> MAVEN IS ON THE WAY. 1020 00:59:44,361 --> 00:59:46,396 >> MAVEN IS THERE. 1021 00:59:46,396 --> 00:59:48,448 XL MARS. 1022 00:59:48,448 --> 00:59:50,316 MRO, ODYSSEY. 1023 00:59:50,316 --> 00:59:52,085 TGO IS ON THE WAY. 1024 00:59:52,085 --> 00:59:54,054 THERE'S SIX AT MARS. 1025 00:59:54,054 --> 00:59:58,208 YES. >> THERE'S A LOT. 1026 00:59:58,208 --> 01:00:02,178 I CAN'T REALLY SPECULATE AS TO WHAT THE NASA PLANNERS ARE DOING 1027 01:00:02,178 --> 01:00:04,297 ABOUT ADDING ANTENNAS. 1028 01:00:04,297 --> 01:00:06,232 I'M SURE THERE ARE PLANS FOR THAT. 1029 01:00:06,232 --> 01:00:09,486 DSAC IS ONE WAY IN WHICH WE CAN USE THE EXISTING NETWORK A LOT 1030 01:00:09,486 --> 01:00:10,487 MORE EFFICIENTLY. 1031 01:00:10,487 --> 01:00:17,127 AND SO, IN THAT ARCHITECTURAL TRADE, THE PLANNERS NEED TO 1032 01:00:17,127 --> 01:00:20,513 DECIDE IS IT MORE COST EFFECTIVE TO PUT A DSAC ON BOARD A 1033 01:00:20,513 --> 01:00:24,517 SPACECRAFT AND EXPAND OUR USER BASE THAT WAY OR ADDING MORE 1034 01:00:24,517 --> 01:00:25,201 ANTENNAS. 1035 01:00:25,201 --> 01:00:28,471 AND I'M SURE THE ANSWER TO THAT WILL DEPEND ON HOW WELL WE ARE 1036 01:00:28,471 --> 01:00:34,127 AT REDUCING THE SIZE OF DSAC AND MAKING IT MORE AFFORDABLE FOR 1037 01:00:34,127 --> 01:00:38,114 MIXED USERS AND PUTTING THAT INTO THE MIX OF THE PLANNING. 1038 01:00:38,114 --> 01:00:44,070 >> SO OUR CURRENT FLEET IS NOT TAXING DSN TO ITS LIMIT, THEN? 1039 01:00:44,070 --> 01:00:45,388 >> NOT RIGHT NOW. >> OKAY. 1040 01:00:45,388 --> 01:00:49,375 >> WHEN I START LOOKING AT THE ARMADA VEHICLES THAT THE HUMAN 1041 01:00:49,375 --> 01:00:52,228 PROGRAM IS CONTEMPLATING, I DON'T KNOW. 1042 01:00:52,228 --> 01:00:58,134 MAYBE THAT COULD CHANGE. >> THE DSN IS A LOT OF -- IT'S 1043 01:00:58,134 --> 01:00:58,284 BUSY. 1044 01:00:58,284 --> 01:01:01,488 DON'T -- THE ANTENNAS ARE -- THEY'RE ALWAYS ON. 1045 01:01:01,488 --> 01:01:04,140 AND THEY'RE ALWAYS TALKING TO SOME SPACECRAFT. 1046 01:01:04,140 --> 01:01:07,460 I'M SURE, IF YOU TALK TO MISSION MANAGERS FOR THESE DIFFERENT 1047 01:01:07,460 --> 01:01:10,430 MISSIONS, THEY WOULD WANT MORE TRACKING TIME THAN THEY GET 1048 01:01:10,430 --> 01:01:11,247 RIGHT NOW. 1049 01:01:11,247 --> 01:01:16,052 SO IT'S DOABLE NOW, BUT IT'S KIND OF GETTING TO BE AT 1050 01:01:16,052 --> 01:01:18,421 CAPACITY. >> IN FACT, I HAVE AN ANECDOTAL 1051 01:01:18,421 --> 01:01:23,076 STORY THAT, WITH THE ARRIVAL OF MAVEN, ODYSSEY WASN'T GETTING AS 1052 01:01:23,076 --> 01:01:27,330 MUCH TRACKING TIME AND THAT WAS STRETCHING THEIR ABILITY TO 1053 01:01:27,330 --> 01:01:31,084 FIGURE OUT THEIR ORBITS TO THE LEVEL THEY NEEDED TO. 1054 01:01:31,084 --> 01:01:33,503 >> THE QUESTION IS WHERE WILL THE LAUNCH TAKE PLACE. 1055 01:01:33,503 --> 01:01:39,425 WE WILL BE LAUNCHED FROM THE HISTORIC PAD 39-A AT THE KENNEDY 1056 01:01:39,425 --> 01:01:45,448 SPACE CENTER, SPACEX IS RENTING THAT FORMER SATURN 5 SHUTTLE PAD 1057 01:01:45,448 --> 01:01:53,072 AND CONVERTING IT FOR THE FALCON HEAVY. 1058 01:01:53,072 --> 01:01:53,256 QUESTION? 1059 01:01:53,256 --> 01:02:04,050 [ INAUDIBLE QUESTION ] >> MERCURY -- 1060 01:02:04,050 --> 01:02:07,036 >> THE QUESTION IS WHY DID WE PICK MERCURY? 1061 01:02:07,036 --> 01:02:09,455 UNFORTUNATELY, I AM NOT AN ATOMIC CLOCK PHYSICIST. 1062 01:02:09,455 --> 01:02:12,475 I CAN ONLY TELL YOU THAT THAT'S WHAT THE GUY WHO KNOWS WHAT HE'S 1063 01:02:12,475 --> 01:02:17,046 DOING SAID TO USE. >> SERIOUSLY, THERE ARE -- IT 1064 01:02:17,046 --> 01:02:23,219 HAS TO DO WITH THE WAY THE ELECTRONS AND THE NUCLEUS TO THE 1065 01:02:23,219 --> 01:02:27,156 ATOM INTERACT AND THE FREQUENCIES AND CAN YOU GET 1066 01:02:27,156 --> 01:02:29,108 PARTS TO GENERATE THE FREQUENCIES. 1067 01:02:29,108 --> 01:02:34,380 IT'S A QUASI PRACTICAL DECISION FOR AN ION TRACK CLOCK. 1068 01:02:34,380 --> 01:02:39,135 THE COMMON CLOCKS LIKE THE GPS SATELLITES HAVE, THEY USE A 1069 01:02:39,135 --> 01:02:45,508 TRANSITION METAL CALLED ROBIDIUM IN A GAS FORM. 1070 01:02:45,508 --> 01:02:50,246 THEY PICKED IT FOR A VARIETY OF PRACTICAL AND PHYSICS REASONS. 1071 01:02:50,246 --> 01:02:54,217 IT USUALLY TURNS OUT TO BE SOMETHING LIKE THAT. 1072 01:02:54,217 --> 01:02:58,371 CZM IS COMMONLY USED IN EARTH-BASED CLOCKS AND LIKEWISE 1073 01:02:58,371 --> 01:03:00,290 THERE ARE PRACTICAL AND HISTORIC REASONS FOR THAT. 1074 01:03:00,290 --> 01:03:03,409 BUT YOU CAN DO IT WITH A WIDE VARIETY OF ATOMS. 1075 01:03:03,409 --> 01:03:07,330 IT JUST DEPENDS ON, REALLY, WHETHER OR NOT YOU CAN -- HOW 1076 01:03:07,330 --> 01:03:12,051 HARD OR EASY IT IS TO ACTUALLY BUILD IT, TO CONSTRUCT IT. 1077 01:03:12,051 --> 01:03:14,404 >> ONE MORE NOTE TO ADD ON PERFORMANCE. 1078 01:03:14,404 --> 01:03:20,376 WE'RE ANTICIPATING THAT THE DSAC THAT WE FLY IS MAYBE FIVE TIMES 1079 01:03:20,376 --> 01:03:25,131 MORE STABLE THAN THE ROBIDIUMS. 1080 01:03:25,131 --> 01:03:30,436 THE OTHER FEATURE OF THE MERCURY CLOCK IS IT DOESN'T DRIFT. 1081 01:03:30,436 --> 01:03:35,441 ON TOP OF RANDOM INSTABILITIES THERE IS USUALLY SOME PSEUDO 1082 01:03:35,441 --> 01:03:38,311 DETERMINISTIC DRIFT THAT PULLS THE CLOCK AWAY. 1083 01:03:38,311 --> 01:03:41,297 ROW BID YUMS INTRINSICALLY HAVE THAT. 1084 01:03:41,297 --> 01:03:42,248 DSAC WILL THAT. 1085 01:03:42,248 --> 01:03:46,185 FACTORING THAT WITH THE INSTABILITY, WE'RE ABOUT 50 1086 01:03:46,185 --> 01:03:54,110 TIMES MORE ACCURATE THAN THE FLYING GPS CLOCKS TODAY. 1087 01:03:54,110 --> 01:03:54,527 >> OKAY. 1088 01:03:54,527 --> 01:03:58,331 I ONLY SEE TWO PEOPLE WE'VE PUT TO SLEEP, SO THAT'S PRETTY GOOD, 1089 01:03:58,331 --> 01:04:00,233 OUT OF THIS CROWD. 1090 01:04:00,233 --> 01:04:03,169 SO ANY OTHER QUESTIONS?