ATS-6

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ATS-6
ATS-6 Satellite
ATS-6 Satellite
ATS-6 satellite.
Mission typeCommunications
Technology
OperatorNASA
COSPAR ID1974-039A Edit this at Wikidata
SATCAT no.07318
Mission duration5 years
Spacecraft properties
BusATS-6 Bus
ManufacturerFairchild Aircraft
Launch mass930.0 kilograms (2,050.3 lb)
Power645 W
Start of mission
Launch dateMay 30, 1974, 23:37:00 (1974-05-30UTC23:37Z) UTC
LC-40
End of mission
DeactivatedJune 30, 1979 (1979-07-01)
Orbital parameters
Reference system
Semi-major axis
41,691.1 kilometres (25,905.6 mi)
Perigee altitude35,184 kilometers (21,862 mi)
Apogee altitude35,444 kilometers (22,024 mi)
Inclination13.1º
Period1,412 minutes
 
ATS-6 during radio-frequency tests.
ATS-6 during radio-frequency tests.

ATS-6 (Applications Technology Satellite-6)

electric propulsion in geostationary orbit. It also carried several particle physics
experiments, including the first heavy ion detector in geostationary orbit.

During its five-year life, ATS-6 transmitted connection programming to various countries, including India, the United States and other regions. The vehicle also conducted air traffic control tests, was used to practice satellite-assisted search and rescue techniques, carried an experimental radiometer subsequently carried as a standard instrument aboard weather satellites, and pioneered direct broadcast TV.

ATS-6 was a precursor to many technologies still in use today on geostationary spacecraft: large deployable antenna, 3-axis attitude control with slewing capabilities, antenna pointing through RF sensing, electric propulsion, meteorological radiometer in geostationary orbit, and direct to home broadcasting. It is also possible that ATS-6 was a forerunner of the large ELINT satellites such as

Mentor
.

Launch

ATS-6 Launch

ATS-6 was launched on May 30, 1974, by a

Titan III-C launch vehicle. The spacecraft was inserted directly in the geosynchronous orbit
. This reduced the on-board fuel requirements to less than 40 kilograms (88 lb) (for a total mass at launch of nearly 1,400 kilograms (3,100 lb)). The highly accurate orbit insertion further lowered the amount of fuel required for final positioning to 9 kilograms (20 lb). This enabled a life extension from the original 2 year to 5 years, even accounting for the premature failure of the electric propulsion subsystem (the station-keeping fuel requirement being around 1.6 kilograms per year (3.5 lb/a)).

ATS-6 inside the Space Environment Simulation Laboratory at the Johnson Space Center (JSC) during antenna deployment tests

Structure, power subsystem and antenna

One of the major innovations of ATS-6 was an in-flight deployable antenna of more than 9 metres (30 ft) in diameter. The antenna reflector was furled during launch under the launch vehicle fairing, and was deployed in orbit much like an umbrella. The antenna reflector was built from 48 aluminum ribs, supporting a metallized

Nickel cadmium batteries
of 15-A·h capacity, powering a regulated 30.5-V bus. The satellite dimensions in orbit were 15.8-metre (52 ft) width by 8.2-metre (27 ft) height.

This deployable antenna parabola was designed and developed by Lockheed Missiles and Space Company (LMSC), now Lockheed Martin, under subcontract to Fairchild Aerospace, after several years of small study contracts at LMSC. The program manager at LMSC was GKC (Colin) Campbell. The deployment of the reflector was initiated by pyrotechnically operated SQUIB cable cutters. Deployment time was on the order of 2.5 seconds producing 3,400 newton-metres (2,500 lb⋅ft) of torque at the spacecraft interface. The reflector surface was designed for optimal operation at S-Band frequencies.[6] It weighed 83 kilograms (182 lb) at launch and stowed into a toroidal volume (doughnut shaped) approximately 1.8 metres (6 ft) in diameter and 250 millimetres (10 in) thick. Three models were fabricated, the STM or structural test model, the F reflector and the G reflector. The STM was destroyed by Fairchild shortly after the program was finished and the F model was launched with the spacecraft in 1972. The G model sat unprotected in the Farchild parking lot for several years before it was donated to the Smithsonian.[citation needed] Bill Wade, the assistant program manager and test manager on the program supported The Smithsonian in the restoration by providing a complete set of drawings and specifications and visited the Silver Hill facility to provide technical guidance.[citation needed]

At the time of launch it was the largest parabolic surface launched into orbit.[citation needed]

Three-axis stabilisation

ATS-6 has been the first geostationary satellite with three-axis stabilization and pointing.,

TDRSS
. This highly advanced (for the time) pointing subsystem used Earth and Sun sensors, a star tracker pointed to the pole star, Polaris, and three inertial sensors. The sensor measurements were fed to two digital computers (nominal and redundant), as well to a back-up analog computer. It was also possible to orient the satellite by using radio-frequency sensors. Actuators were three momentum wheels, and hot gas (hydrazine mono-propellant) thrusters. One of the momentum wheels having failed in July 1975, an alternative scheme was developed, allowing station-keeping with the two remaining wheels and thrusters.

Electric propulsion

ATS-6 was equipped with two electric thrusters based on the acceleration of cesium ions, that were to be used for North-South Station Keeping.[10] This subsystem development followed earlier failed attempts on the previous ATS spacecraft. Each of the thrusters had a mass of 16 kilograms (35 lb), used 150 W of electric power, and produced a thrust of 4 newton-metres (3.0 lbf⋅ft), with a specific impulse of 2500s. The on-board supply of cesium would have been sufficient for 4400 hours of thrust. Unfortunately, both thrusters failed prematurely, one after 1 hour of operation, one after 95 hours. However, some of the experiments objectives could be met, such as the measurement of the effective thrust, the absence of any interference with the radio-frequency payloads (from 150 MHz to 6 GHz), no cesium redeposition on the critical parts of the payload (such as the radiometer), and the correct neutralisation of the spacecraft versus its environment.

Payload

Radiometer

A radiometer was on board ATS-6, mounted on the earth-facing panel.[11] This instrument was (for the time) of very high resolution. It operated on two channels: infra-red (10.5 to 12.5 μm) and visible light (0.55 to 0.75 μm). Images taken with the radiometer covered the whole earth disk, with a resolution of 1,200 lines of 2,400 pixels each (11-kilometre (6.8 mi) square pixel in infra-red, and 5.5-kilometre (3.4 mi) square in visible light). The IR detector was passively cooled at 115K, and the visible light detector maintained at 300K. A complete image of earth's disk was transmitted to ground every 25 minutes. Several hundreds images were taken and transmitted, until a mechanical component of the radiometer failed, two and a half months after launch.

Telecommunication experiments

Zone covered by the SITE Experiment

The main mission of ATS-6 was to demonstrate the feasibility of direct-to-home (

Apollo-Soyuz flight
.

Particle physics experiments

Several particle physics experiments were on board ATS-6. The most significant measured low energy protons (from 25 keV to 3.6 MeV),[16] as well as detected heavy ions (up to 6 MeV). This latter experiment allowed to detect the first heavy ions (Z > 6) with an energy E > 4 MeV, in geostationary orbit.

Propagation experiments

Finally, ATS-6 embarked several radio beacons,[17] which allowed to measure electromagnetic propagation properties of the atmosphere at 13, 18, 20 and 30 GHz.

Decommissioning

By June 30, 1979, only one of the four ATS-6 station keeping thrusters was working, and was showing signs of unreliability. This thruster was used to move ATS-6 out of geostationary orbit to an orbit several hundred kilometers higher. This was to vacate the geostationary slot for the next satellite.[18]

See also

References

  1. ^ McDowell, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved January 24, 2014.
  2. ^ ATS-6 Significance, R.B. Marsten IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  3. ^ "table4.156". nasa.gov. Retrieved March 22, 2015.
  4. ^ Glover, Daniel R. (1996). "NASA Experimental Communications Satellites, 1958-1995". Beyond the Ionosphere. NASA.
  5. ^ http://hdl.handle.net/2060/19820008279 ATS-6 engineering performance report. Volume 6: Scientific experiments
  6. ^ Wales, Robert O. (November 1981). "ATS-6 Final Engineering Performance Report" (PDF). NASA. pp. 76–78. Retrieved February 4, 2023.
  7. ^ ATS-6 Spacecraft Attitude Precision Pointing & Slewing Adaptative Control Experiment, W.C. Isley; D.L. Endres IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  8. ^ ATS-6 Interferometer, W.C. Isley; D.L. Endres IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  9. ^ Orbit Determination Accuracies Using Satellite-to-Satellite Tracking, F.O. Vonbun; P.D. Argentiero; P.E. Schmid IEEE transactions on Aerospace & Electronic Systems vol.AES-14 N°6
  10. ^ ATS-6 Cesium Bombardment engine North South Station Keeping Experiment, R.M. Worlock; E. James; R.E. Hunter; R.O. Bartlett IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  11. ^ ATS-6 The Very High Resolution Radiometer, W.E. Shenk; C.C Stephanides; G.E. Sonnek; L.D. Howell IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  12. ^ A Dream Come True: Satellite Broadcasting, R. Marsten IEEE transactions on Aerospace & Electronic Systems vol.33 N°1
  13. , P56
  14. , P56
  15. ^ ATS-6 Satellite Instructional Television Experiment J.E. Miller, IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  16. ^ NOAA Low Energy Proton Experiment, T.A. Fritz; J.A. Cessna IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  17. ^ ATS-6 Millimeter Wave Propagation and Communication Experiments, L.I. Ippolito IEEE transactions on Aerospace & Electronic Systems vol.AES-11 N°6
  18. P57

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