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Transit 4B

NSSDCA/COSPAR ID: 1961-031A

Description

Transit 4B was a US Navy navigation satellite launched by a Thor Able Star rocket. It carried a SNAP 3 nuclear power source. Transit, one of the first operational satellite systems, was also known as the Navy Navigation Satellite (NNS). It was launched from Cape Canaveral on 15 November 1961 at 22:19 UT along with the TRAAC satellite. It failed on 2 August 1962 due to radiation damage sustained by the solar cells from the Starfish Prime high altitude nuclear test explosion on 9 July 1962.

The Transit spacecraft were developed for updating the inertial navigation systems on board US Navy Polaris submarines, and later for civilian use. Transit receivers used the known characteristics of the satellite's orbit, measured the Doppler shift of the satellite's radio signal, and thereby calculated the receivers position on the earth. As a single spacecraft travelled overhead, the user measured the Doppler shift over a 15 minute period by receiving timing marks and satellite orbital information on two separate frequencies, 149.99 and 399.97 MHz. These signals were corrected for ionospheric refraction and the information was then fed into the users navigation system.

Individual Transit satellites operated for over 10 years. Technical break- throughs during the program included gravity gradient stabilization, the use of radio-isotope thermoelectic generators (RTG), and navigation satellite technologies later used in the GPS system. Transit was superseded by the Navstar global positioning system. The use of the satellites for navigation was discontinued at the end of 1996 but the satellites continued transmitting and became the Navy Ionospheric Monitoring System (NIMS).

Starfish Prime

Starfish Prime was an American high-altitude nuclear test that took place on 9 July 1962. Launch took place from Johnston atoll in the Pacific Ocean (about 1330 km southwest of Honolulu) at 8:46:28 UT on 9 July 1962 (10:46:28 pm, 8 July local time) on a Thor rocket carrying a W49 thermonuclear warhead. Detonation of the warhead occurred at 09:00:09 UT on 9 July (11:00:09 pm local time, 8 July) at an altitude of 400 km. Total yield was 1.4 megatons. The explosion, occurring at a geomagnetic latitude 10.5 degrees, generated an electromagnetic pulse and generated large amounts of charged particles. These had the effect of damaging many operating satellites, both at the time of the blast and later, as the energetic particles remained trapped in the Earth's magnetic field, forming an artificial radiation belt that persisted for many days after the explosion. These damaged satellites include TRAAC, Transit-4B, Ariel 1, Cosmos 5, Telstar 1, Explorers 14 and 15, and possibly Injun 1, OSO-1, Alouette 1, and ANNA-1B.

Image credit: National Museum of the U.S. Navy

Alternate Names

  • 00202
  • 1961 Alpha Eta 1
  • Transit4B

Facts in Brief

Launch Date: 1961-11-15
Launch Vehicle: Thor-Able-Star
Launch Site: Cape Canaveral, United States
Mass: 86 kg

Funding Agency

  • Department of Defense-Department of the Navy (United States)

Discipline

  • Navigation/Global Positioning

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office

 
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