1 00:00:00,280 --> 00:00:02,000 Speaker 1: The Day in History Class is a production of I 2 00:00:02,080 --> 00:00:06,920 Speaker 1: Heart Radio. Hey everyone, welcome to the podcast I'm Eves 3 00:00:07,000 --> 00:00:09,600 Speaker 1: and you're listening to this Day in History Class, a 4 00:00:09,680 --> 00:00:12,319 Speaker 1: podcast that really takes to heart the phrase you learn 5 00:00:12,440 --> 00:00:24,880 Speaker 1: something new every day. Today is October four. The day 6 00:00:25,000 --> 00:00:29,920 Speaker 1: was October four, ninety seven. The Soviet Union launched the 7 00:00:30,000 --> 00:00:34,840 Speaker 1: first artificial Earth satellite, and scientists at the Massachusetts Institute 8 00:00:34,840 --> 00:00:38,720 Speaker 1: of Technology noticed that the frequency of its radio signal 9 00:00:38,920 --> 00:00:42,400 Speaker 1: increased as it moved closer and decreased as it moved 10 00:00:42,479 --> 00:00:47,000 Speaker 1: farther away. This discovery led scientists to study how they 11 00:00:47,000 --> 00:00:51,080 Speaker 1: could use satellites to locate receivers on Earth, an idea 12 00:00:51,159 --> 00:00:54,360 Speaker 1: that marked the beginning of the development of satellite navigation 13 00:00:54,400 --> 00:01:00,520 Speaker 1: systems and eventually GPS. After spot Nick launched, two physicist 14 00:01:00,640 --> 00:01:04,920 Speaker 1: at Johns Hopkins Applied Physics Laboratory, doctors William Geyer and 15 00:01:04,959 --> 00:01:09,959 Speaker 1: George Wifenbach, tracked the satellite using the Doppler effect. The 16 00:01:10,000 --> 00:01:13,199 Speaker 1: Doppler effect is the change in frequency or a wavelength 17 00:01:13,360 --> 00:01:16,759 Speaker 1: of a wave as the waves source and its observer 18 00:01:17,040 --> 00:01:20,760 Speaker 1: move toward or away from each other. A familiar illustration 19 00:01:20,800 --> 00:01:23,240 Speaker 1: of the Doppler effect is the change in pitch of 20 00:01:23,280 --> 00:01:28,480 Speaker 1: sirens as an emergency vehicle approaches and passes by. Chairman 21 00:01:28,520 --> 00:01:32,919 Speaker 1: of the Applied Physics Laboratories Research Center, Frank McClure, suggested 22 00:01:33,120 --> 00:01:36,600 Speaker 1: that if the satellite position is known, then a navigator 23 00:01:36,600 --> 00:01:40,319 Speaker 1: on Earth could receive and process the satellite signal to 24 00:01:40,400 --> 00:01:44,240 Speaker 1: determine their location. This led to the creation of the 25 00:01:44,280 --> 00:01:50,120 Speaker 1: TRANSIT system, the first satellite based geo positioning system. TRANSIT 26 00:01:50,200 --> 00:01:52,680 Speaker 1: was developed by the a p L and the Defense 27 00:01:52,760 --> 00:01:58,120 Speaker 1: Advanced Research Projects Agency, and it was sponsored by the U. S. Navy. 28 00:01:58,760 --> 00:02:01,640 Speaker 1: Its main purpose was to provide location updates to the 29 00:02:01,720 --> 00:02:06,000 Speaker 1: Navy's ballistic missile submarines, but it was also used as 30 00:02:06,000 --> 00:02:11,160 Speaker 1: a navigation system for surface ships and for surveying. TRANSIT 31 00:02:11,320 --> 00:02:15,600 Speaker 1: was fully operational by nineteen sixty four. In nineteen sixty seven, 32 00:02:15,760 --> 00:02:21,040 Speaker 1: Transit became available for civilian use, but scientists realized that 33 00:02:21,120 --> 00:02:24,520 Speaker 1: a more accurate navigation system that could operate all day, 34 00:02:24,639 --> 00:02:29,000 Speaker 1: every day would be better than TRANSIT. Transit had high 35 00:02:29,000 --> 00:02:33,720 Speaker 1: accuracy compared to other navigation systems, but it still had limitations. 36 00:02:34,440 --> 00:02:37,920 Speaker 1: The technology and techniques developed for TRANSIT contributed to the 37 00:02:37,960 --> 00:02:43,160 Speaker 1: introduction of the Global Positioning System or GPS. So did 38 00:02:43,160 --> 00:02:48,680 Speaker 1: the development of other programs like Tomation and but by 39 00:02:48,720 --> 00:02:52,639 Speaker 1: the early nineteen seventies, US defense officials realized that it 40 00:02:52,680 --> 00:02:56,400 Speaker 1: would be advantageous to have a single satellite based navigation 41 00:02:56,480 --> 00:03:00,760 Speaker 1: system with several military applications by other than having a 42 00:03:00,800 --> 00:03:05,600 Speaker 1: bunch of expensive ones. The first operational GPS satellite was 43 00:03:05,680 --> 00:03:10,240 Speaker 1: launched in nineteen seventy eight, and by ninete GPS reached 44 00:03:10,280 --> 00:03:15,080 Speaker 1: initial operational capability with a full constellation of twenty four satellites. 45 00:03:16,240 --> 00:03:20,760 Speaker 1: Two years later, GPS became fully operational with twenty seven satellites, 46 00:03:21,160 --> 00:03:25,440 Speaker 1: three of which were spares. From the beginning, GPS was 47 00:03:25,520 --> 00:03:28,400 Speaker 1: a dual use system, meaning that it was made for 48 00:03:28,480 --> 00:03:33,520 Speaker 1: civilian and military use. The Transit System ended its navigation 49 00:03:33,560 --> 00:03:38,080 Speaker 1: service in nine six since GPS technology had improved greatly 50 00:03:38,200 --> 00:03:42,440 Speaker 1: and deemed it obsolete, and in two thousand the Defense 51 00:03:42,520 --> 00:03:46,480 Speaker 1: Department ended the selective availability of GPS, which meant that 52 00:03:46,520 --> 00:03:50,080 Speaker 1: it was no longer purposefully degrading the signal for civilian users. 53 00:03:51,200 --> 00:03:54,600 Speaker 1: GPS receivers now have a much higher accuracy than they 54 00:03:54,680 --> 00:03:59,040 Speaker 1: did at the time of this switch. As GPS technology advanced, 55 00:03:59,160 --> 00:04:02,360 Speaker 1: it became of a doable and more personal products like 56 00:04:02,560 --> 00:04:07,200 Speaker 1: car navigation devices and cell phones. I'm Eve stepf Coote 57 00:04:07,200 --> 00:04:09,640 Speaker 1: and hopefully you know a little more about history today 58 00:04:09,640 --> 00:04:13,040 Speaker 1: than you did yesterday. You can find us on social 59 00:04:13,080 --> 00:04:17,839 Speaker 1: media at t d i h C Podcast on Twitter, Instagram, 60 00:04:17,880 --> 00:04:21,840 Speaker 1: and Facebook, and you can email us at this Day 61 00:04:22,080 --> 00:04:27,120 Speaker 1: at i heart media dot com. Thanks again for listening, 62 00:04:27,200 --> 00:04:30,320 Speaker 1: and have a fantastic twenty four hours until we see 63 00:04:30,320 --> 00:04:44,560 Speaker 1: you again. For more podcasts from I Heeart Radio, visit 64 00:04:44,560 --> 00:04:47,240 Speaker 1: the iHeart Radio app, Apple Podcasts, or wherever you listen 65 00:04:47,279 --> 00:04:48,120 Speaker 1: to your favorite shows.