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Automatic Picture Transmission (APT) System

NSSDCA ID: 1966-040A-02

Mission Name: Nimbus 2
Principal Investigator:Mr. Joseph R. Schulman

Description

The Nimbus 2 Automatic Picture Transmission (APT) system was a camera and transmitter combination designed to transmit local daytime slow-scan television pictures of cloudcover conditions to properly equipped ground receiving stations on a real-time basis. The camera used a 108-deg wide-angle f/1.8 objective lens with a focal length of 6.0 mm. The camera was mounted facing earthward on the H-frame inside the sensory ring, with its optical axis parallel to the spacecraft spin axis. The actual photography required 8 s and the transmission 200 s. Earth-cloud images retained on the photosensitive surface of the 2.54-cm-diameter vidicon were read out at four lines per second to produce an 800-line picture. A 5-W TV transmitter (137.5 MHz) relayed the pictures to local APT stations within communication range. The faceplate of the vidicon had reticle marks that appeared on the picture format to aid in relating the picture to its geographical position on the earth's surface. From the satellite attitude and altitude (approximately 1100 km), a picture covered a 1200- by 1200-km square with a horizontal resolution of better than 3 km at nadir. The APT system was capable of transmitting the nighttime high-resolution infrared radiometer (HRIR) sensor output through the APT transmitter. Hence, with some minor modifications, an APT station within telemetry range could receive HRIR data in the direct readout infrared radiometer (DRIR) mode. The experiment was a success, and good data were obtained during its operational lifetime. More detailed information can be found in Section 5 of the "Nimbus II Users' Guide" (TRF B03406), available from NSSDC. APT/DRIR data are primarily intended for operational use within the local APT acquisition station and are generally not available for distribution.

Alternate Names

  • APT
  • Nimbus2/APT

Funding Agency

  • Department of Defense-Department of the Air Force (United States)

Discipline

  • Earth Science: Atmospheric Dynamics

Additional Information

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

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. Joseph R. SchulmanPrincipal InvestigatorNASA Goddard Space Flight Center
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