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Transit 3B / LOFTI 1



The LOFTI 1 and Transit 3B satellites were attached at launch and failed to separate after deployment owing to a programmer malfunction during launch. The orbit was more elliptical than the planned circular orbit, which shortened the satellite's lifetime to 37 days. Satellite transmitters functioned normally, and signals were received although the elliptical orbit decreased the value of the data.


The LOFTI (LOw Frequency Trans-Ionospheric) satellite configuration (pictured at left) consisted of a 25.9-kg aluminum-covered sphere with a diameter of 50.8 cm. It was mounted piggyback on the Transit 3B satellite. The two satellites were designed to separate after injection into orbit. The smaller LOFTI was a low-frequency trans-ionospheric satellite that was designed to explore low-frequency radio wave propagation through the ionosphere. The satellite was powered by nickel-cadmium batteries that were charged by six circular groups of solar cells arranged around the surface of the sphere. On top of the sphere was a VLF loop antenna in the form of a a near-circular band with a mean diameter of about , and a guide tube for an extensible 460 cm whip antenna. A second 460 cm whip antenna was deployed through an orifice in the bottom of the sphere. Situated at 90 degree intervals around the equator of the sphere were four telemetry antenna rods. Also mounted on the equator were four photoelectric solar aspect sensors, and just below these four tubes containing photoelectric Earth aspect sensors. LOFTI contained a telemetry system, a 136.17-MHz transmitter, a command receiver, and two VLF receivers for 18-KHz signals from a VLF transmitter (NBA) in the Panama Canal zone.

Transit 3B

The Transit 3B satellite (pictured below) had a mass of 113-kg and was spherical in shape with a 91.4-cm diameter. It was powered by nickel-cadmium batteries charged by 6600 solar cells. It contained instruments for advanced development of an all-weather global navigation system for surface craft, submarines, and aircraft. Transit 3B contained two transmitting systems, a command system, a despin system, and electronic clock, a telemetry system, and a digital memory system for storing orbital data from ground stations to compute an accurate navigational fix. A SECOR (SEquential COllation of Range) transponder was carried as part of a new geodetic survey system.

Image of LOFTI satellite credit: National Museum of the U.S. Navy; Transit 3B image credit: R.R. Simmons

Alternate Names

  • 00087
  • 1961 Eta 1
  • LOFTI 1
  • Transit3B

Facts in Brief

Launch Date: 1961-02-22
Launch Vehicle: Thor
Launch Site: Cape Canaveral, United States
Mass: 600 kg

Funding Agency

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


  • Navigation/Global Positioning

Additional Information

Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Transit 3B

Lofti 1 model at the Smithsonian Air and Space Udvar-Hazy Center.

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