Sputnik's launch inspired satellite navigation systems - October 4, 1957

On this day, the Soviets launched Sputnik, which inspired scientists to begin using satellites to create navigation systems. 

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:00):
The Day in History Class is a production of I
Heart Radio. Hey everyone, welcome to the podcast I'm Eves
and you're listening to this Day in History Class, a
podcast that really takes to heart the phrase you learn
something new every day. Today is October four. The day

(00:25):
was October four, ninety seven. The Soviet Union launched the
first artificial Earth satellite, and scientists at the Massachusetts Institute
of Technology noticed that the frequency of its radio signal
increased as it moved closer and decreased as it moved
farther away. This discovery led scientists to study how they

(00:47):
could use satellites to locate receivers on Earth, an idea
that marked the beginning of the development of satellite navigation
systems and eventually GPS. After spot Nick launched, two physicist
at Johns Hopkins Applied Physics Laboratory, doctors William Geyer and
George Wifenbach, tracked the satellite using the Doppler effect. The

(01:10):
Doppler effect is the change in frequency or a wavelength
of a wave as the waves source and its observer
move toward or away from each other. A familiar illustration
of the Doppler effect is the change in pitch of
sirens as an emergency vehicle approaches and passes by. Chairman
of the Applied Physics Laboratories Research Center, Frank McClure, suggested

(01:33):
that if the satellite position is known, then a navigator
on Earth could receive and process the satellite signal to
determine their location. This led to the creation of the
TRANSIT system, the first satellite based geo positioning system. TRANSIT
was developed by the a p L and the Defense
Advanced Research Projects Agency, and it was sponsored by the U. S. Navy.

(01:58):
Its main purpose was to provide location updates to the
Navy's ballistic missile submarines, but it was also used as
a navigation system for surface ships and for surveying. TRANSIT
was fully operational by nineteen sixty four. In nineteen sixty seven,
Transit became available for civilian use, but scientists realized that

(02:21):
a more accurate navigation system that could operate all day,
every day would be better than TRANSIT. Transit had high
accuracy compared to other navigation systems, but it still had limitations.
The technology and techniques developed for TRANSIT contributed to the
introduction of the Global Positioning System or GPS. So did

(02:43):
the development of other programs like Tomation and but by
the early nineteen seventies, US defense officials realized that it
would be advantageous to have a single satellite based navigation
system with several military applications by other than having a
bunch of expensive ones. The first operational GPS satellite was

(03:05):
launched in nineteen seventy eight, and by ninete GPS reached
initial operational capability with a full constellation of twenty four satellites.
Two years later, GPS became fully operational with twenty seven satellites,
three of which were spares. From the beginning, GPS was
a dual use system, meaning that it was made for

(03:28):
civilian and military use. The Transit System ended its navigation
service in nine six since GPS technology had improved greatly
and deemed it obsolete, and in two thousand the Defense
Department ended the selective availability of GPS, which meant that
it was no longer purposefully degrading the signal for civilian users.

(03:51):
GPS receivers now have a much higher accuracy than they
did at the time of this switch. As GPS technology advanced,
it became of a doable and more personal products like
car navigation devices and cell phones. I'm Eve stepf Coote
and hopefully you know a little more about history today
than you did yesterday. You can find us on social

(04:13):
media at t d i h C Podcast on Twitter, Instagram,
and Facebook, and you can email us at this Day
at i heart media dot com. Thanks again for listening,
and have a fantastic twenty four hours until we see
you again. For more podcasts from I Heeart Radio, visit

(04:44):
the iHeart Radio app, Apple Podcasts, or wherever you listen
to your favorite shows.