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Interrogation, Recording, and Location System

NSSDC ID: 1969-037A-07 Mission Name: Nimbus 3

Principal Investigator: Mr. Charles E. Cote

The Nimbus 3 interrogation, recording, and location system (IRLS) experiment was designed to collect and retransmit meteorological, geophysical, and other experimental data from remote unmanned data collection stations (platforms) deployed on a global scale.
The IRLS could also determine the location and track the movement of such platforms as balloons, ocean buoys, and ships to within an accuracy of 2 km.
The IRLS consisted of:

(1) a 466-MHz receiver,
(2) a 401.5-MHz transmitter,
(3) decoding and coding circuits,
(4) a range detector, and
(5) a 20-kb satellite data memory capable of storing data measurements during each orbit for up to 20 different interrogations.

On each orbital pass, when the satellite was within range of an acquisition and command station, the satellite command memory was programmed to communicate with selected platforms during the coming orbit. The satellite stored both the address (number) of each platform and the desired time that each should be contacted. At the appropriate time in orbit, the satellite interrogated each platform, measured the satellite to platform distance by determining the round trip propagation time of the rf signal, received the analog data from the platform, converted it to digital form, and stored it. Upon return to the locale of the ground station, the station commanded the satellite to transmit the stored data and to accept new commands for the next orbit.

The experiment was successful and functioned normally from launch until September 1970, when the operational capacity was severely restricted by spacecraft yaw problems. All data acquistion ceased on January 22, 1972, when spacecraft operations were terminated.

Copies of computer printouts from individual platform experiments are retained at the Nimbus/ATS Data Utilization Center, NASA-GSFC, Greenbelt, MD.