Air Density Explorer

Explorer 24 (Air Density C)

Start of Explorer 9 on a Scout-X1

The Air Density Explorer series (originally known as S-56 hereinafter) were balloon satellite , in the context of the Explorer program of NASA were launched to the density of the upper atmosphere to be measured.

construction

The balloon skin consisted of alternating layers of aluminum and plastic foil . Numerous white 5 cm circles were attached to the outermost aluminum skin in order to stabilize the surface temperature . A small transmitter on 136.620 MHz - operated by four solar cells - used the electrical polarity of the two balloon hemispheres as an antenna. The diameter of the inflated balloon was 366 cm.

The current orbit determination , which was crucial for the mission, was therefore taken over by the network of 12 Baker-Nunn cameras . The visual moonwatch stations organized by SAO (around 100 teams of amateur astronomers on all continents) also contributed significantly to the success of the research project .

The brightness of the satellites corresponded to about a third mag star , so that it could be observed near the perigee even at dusk, where the satellite cameras had to stop.

Various versions of the Scout were used as a launch rocket . The takeoffs were from the Wallops Flight Facility and Vandenberg Air Force Base . Due to the low mass of the satellites, they were launched from the fourth launch as secondary payloads with other satellites in order to be able to use the capacity of the launch vehicles more effectively.

Missions

S-56 did not go into orbit because the second stage of the launcher did not fire.

Explorer 9 ( S-56a, Air Density 1 ) was a repeat of the first mission. This time the satellite went into orbit and unfolded as planned. Explorer 9 burned up on April 9, 1964 .

Explorer 19 ( Air Density A ) was launched successfully, but the apogee did not quite reach the planned altitude. Since the transmitter did not work satisfactorily either, it could hardly be received by the ground stations (especially minitrack - Doppler measurements ). At the start, Explorer 9 was still in its orbit, so that simultaneous measurements of the air density in two very different orbit ellipses were possible. The balloon burned up on May 10, 1981.

Explorer 24 ( Air Density B ) was launched together with the ionospheric research satellite Explorer 25 (IE B). The satellite burned up on October 18, 1968.

Explorer 39 ( Air Density C ) was launched together with the ionospheric research satellite Explorer 40 (IE C). Explorer 39 burned up on June 22, 1981. The tracking devices failed as early as June 1971.

DAD B ( Dual Air Density B ) should be launched with the atmospheric research satellite DAD A. Due to a failure of the launcher, both payloads did not enter orbit. In the event of a successful start, DAD B would have been named Explorer 57 .

overview

Explorer	Surname	Start date	Launch rocket	Starting place	Orbit ( apogee , perigee , inclination )	Dimensions	Re-entry	description
Explorer (9)	P.56	4th December 1960	Scout-X1	WI	False start	6.3 kg	---
Explorer 9	S-56a	February 16, 1961	Scout-X1	WI	634 km 2,583 km 38.86 °	7 kg	April 9, 1964
Explorer 19	AD-A	December 19, 1963	Scout-X4	Va	590 km 2,394 km 78.62 °	7.7 kg	May 10, 1981
Explorer 24	AD-B	November 21, 1964	Scout-X4	Va	525 km 2,498 km 81.36 °	8.6 kg	October 18, 1968	with Explorer 25 launched
Explorer 39	AD-C	August 8, 1968	Scout-B	Va	670 km 2,538 km 80.66 °	9.4 kg	June 22, 1981	with Explorer 40 launched
Explorer (57)	DAD-B	5th December 1975	Scout F1	Va	False start	9 kg	---	with DAD-A started

See also

• Day observation , echo 1 , stellar triangulation
• Aeronomy , satellite geodesy

swell

• S 56 in the NASA master catalog
• Explorer 9 (S 56a) in the NASA master catalog
• Explorer 19 (AD A) in the NASA master catalog
• Explorer 24 (AD B) in the NASA master catalog
• Explorer 39 (AD C) in the NASA master catalog
• DAD B in the NASA master catalog
• Air Density Explorer at space.skyrocket.de
• Hayes, Trackers of the Sky . An History of Moonwatch, Massachusetts ~ 1975.