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DAD A (Explorer (56))


The DAD A (Dual Air Density Explorer-A) satellite was a 0.76 m rigid sphere designed to determine, in conjunction with DAD B (Dual Air Density Explorer-B), the vertical structure of the upper thermosphere and the lower exosphere as a function of latitude, season, and local solar time. Both satellites would have been launched by a single Scout-F1 launch vehicle into coplanar polar orbits. Measurements of atmospheric density from DAD-A would have been obtained from satellite drag analyses near perigee (approximately 350 km) and from composition measurements taken by an onboard mass spectrometer. DAD-A was equipped with a radio beacon to facilitate tracking.

The Atmospheric Composition Mass Spectrometer experiment on DAD-A was designed to perform composition measurements in the upper thermosphere (approximately 350 km). The instrument was a magnetic mass spectrometer with a Mattauch-Herzog geometry and would have measured the distribution of such atmospheric constituents as oxygen, mitrogen, helium, hydrogen, neon, and argon.

The atmospheric drag density experiment on DAD-A was designed to provide indirect measurements of upper thermospheric density near satellite perigee (approximatley 350 km). The experiment had no unique onboard hardware. The density values would have been derived from sequential observations of the satellite's position. The experiment would have yielded systematic values of atmospheric density as a function of latitude, season, and local solar time.

The launch of the DAD satellites failed on 6 December 1975.

Nation: USA
Type / Application: Research
Operator: NASA
Contractors: NASA Langley Research Center
Equipment: Atmospheric Composition Mass Spectrometer, atmospheric drag density experiment, radio beacon
Configuration: Sphere
Propulsion: None
Power: Solar cells, batteries
Mass: 40 kg
Satellite COSPAR Date LS Launch Vehicle Remarks
Explorer (56) (DAD A, DADE A) 1975-F06 06.12.1975 Va SLC-5 F Scout-F1 with DAD B


  • NSSDC Master Catalog: DADE-A
Further Explorer missions:

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