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TETR 4 (Test and Training Satellite 4), NASA's third successful orbiting target, was launched into orbit from the Eastern Test Range (ETR) at 0945 UT on September 29, 1971, piggyback with the OSO 7 satellite on a Delta-N launch vehicle. The 20-kg octahedral (0.30 m wide) satellite, which carried a transponder to transmit and receive S-band data signals simulating Apollo spacecraft, was housed on the second stage of the lanuch vehicle and was ejected to the rear approximately 1 minute after third stage ignition into a slightly elliptical orbit (apogee 571 km, perigee 400 km).

The objectives of the spacecraft were to check out manned space flight network stations before the Apollo 16 mission, to help train ground personnel, to simulate routine all-weather missions, and to develop and verify target acquisition and handover techniques using the S-band system.

The tracking beacon and telemetry transmitted continuously on 136.62 MHz at 0.5 W and 2282.5 MHz at 0.5 W.

As of October 1972, the satellite was being tracked on the 136.62-MHz band by minitrack and ground controllers were receiving good telemetry. However, owing to damage possibly sustained by the satellite during third stage separation, the normal mode of sending commands to TETR 4 had not been successful.

Alternate Names

  • 05492
  • TETR-D
  • TETR4

Facts in Brief

Launch Date: 1971-09-29
Launch Vehicle: Delta
Launch Site: Cape Canaveral, United States
Mass: 20.4 kg

Funding Agency

  • NASA-Office of Manned Space Flight (United States)


  • Engineering

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. Charles H. UnderwoodProject ManagerNASA Goddard Space Flight Center
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