Encyclopedia Astronautica
SCATHA


American communications technology satellite. One launch, 1979.01.30.

SCATHA's primary mission was to obtain information about the processes and effects of spacecraft charging, a phenomenon known to have contributed to several on-orbit satellite failures. The mission's specific objectives were to (1) obtain environmental and engineering data to allow the creation of design criteria, materials, techniques, tests and analytical methods to control charging of spacecraft surfaces and (2) collect scientific data about plasma wave interactions, substorms, and the energetic ring. (Spacecraft shown in stowed configuration, with experiment booms stowed). The spacecraft was also known as P78-2.

The spacecraft was spin stabilized (~1 rpm) with 5 deg pointing accuracy. The hydrazine propulsion system had 8 thrusters and 2 tanks. Body mounted solar cells generated 290 watts and recharged three 8 Ahr NiCd batteries. Downlink was at 8.2 kbps at S-Band from redundant 10 W transmitters. The aluminum, titanium, magnesium, and glass fiber structure supported seven deployed experiment booms. Two tape recorders provided ~350 Mb storage each.

The twelve experiments had a total mass of 87 kg and consumed 110 W. They were:

  • SC1 - Engineering Experiments plus VLF and HF Receivers - measured surface potentials of various spacecraft materials, measured RF waves between 0-300 kHz, 2-30 Mhz.
  • SC2 Spacecraft Sheath Fields Plus Energetic Ions - measured low energy electrons and ions, energetic protons, and electrons.
  • SC3 High Energy Particle Spectrometer - measured high energy electrons and protons.
  • SC4 Satellite Electron and Positive Ion Beam System - used ion and electron beam guns to control spacecraft surface potential.
  • SC5 Rapid Scan Particle Detector - measured electrons and ions.
  • SC6 Thermal Plasma Analyzer (failed soon after initial turn on) - designed to measure thermal electrons and ions.
  • SC7 Light Ion Mass Spectrometer (failed soon after initial turn on) - designed to measure light ion density, temperature and composition.
  • SC8 Energetic Ion Compositions Experiment - measured low energy electrons and the ion composition of energetic plasma.
  • SC9 UCSD Charged Particle Experiment - measured electrons and ions.
  • SC10 Electric Field Detector - measured DC and ELF electric fields and satellite potential.
  • SC11 Magnetic Field Monitor - measured DC and ELF magnetic fields.
  • ML12 Spacecraft Contamination Plus Thermal Control Materials Monitoring -measured contamination rates and property changes of several thermal control material samples.
  • TPM Transient Pulse Monitor - supported the other experiments by providing supporting data about the electromagnetic pulse environment.

AKA: Spacecraft Charging at High Altitude.
Gross mass: 360 kg (790 lb).
Height: 1.80 m (5.90 ft).
First Launch: 1979.01.30.
Number: 1 .

More... - Chronology...


Associated Countries
See also
  • Delta The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Development began in 1955 and it continued in service in the 21st Century despite numerous candidate replacements. More...

Associated Launch Vehicles
  • Delta American orbital launch vehicle. The Delta launch vehicle was America's longest-lived, most reliable, and lowest-cost space launch vehicle. Delta began as Thor, a crash December 1955 program to produce an intermediate range ballistic missile using existing components, which flew thirteen months after go-ahead. Fifteen months after that, a space launch version flew, using an existing upper stage. The addition of solid rocket boosters allowed the Thor core and Able/Delta upper stages to be stretched. Costs were kept down by using first and second-stage rocket engines surplus to the Apollo program in the 1970's. Continuous introduction of new 'existing' technology over the years resulted in an incredible evolution - the payload into a geosynchronous transfer orbit increasing from 68 kg in 1962 to 3810 kg by 2002. Delta survived innumerable attempts to kill the program and replace it with 'more rationale' alternatives. By 2008 nearly 1,000 boosters had flown over a fifty-year career, and cancellation was again announced. More...
  • Delta 2914 American orbital launch vehicle. Four stage vehicle consisting of 9 x Castor 2 + 1 x ELT Thor/RS-27 + 1 x Delta P /TR-201 + 1 x Star 37E More...
  • Delta 2000 American orbital launch vehicle. The Delta 2000 series used Castor 2 strap-ons together with an Extended Long Tank core equipped with the more powerful RS-27 engine. This engine was derived from surplus H-1 engines intended for the Saturn IB booster of the Apollo programme. The Delta P upper stage was built by Douglas and used surplus Apollo lunar module engines from TRW. More...

Associated Manufacturers and Agencies
  • USAF American agency overseeing development of rockets and spacecraft. United States Air Force, USA. More...
  • Martin American manufacturer of rockets, spacecraft, and rocket engines. Martin Marietta Astronautics Group (1956), Denver, CO, USA. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
  • McDowell, Jonathan, Launch Log, October 1998. Web Address when accessed: here.

Associated Launch Sites
  • Cape Canaveral America's largest launch center, used for all manned launches. Today only six of the 40 launch complexes built here remain in use. Located at or near Cape Canaveral are the Kennedy Space Center on Merritt Island, used by NASA for Saturn V and Space Shuttle launches; Patrick AFB on Cape Canaveral itself, operated the US Department of Defense and handling most other launches; the commercial Spaceport Florida; the air-launched launch vehicle and missile Drop Zone off Mayport, Florida, located at 29.00 N 79.00 W, and an offshore submarine-launched ballistic missile launch area. All of these take advantage of the extensive down-range tracking facilities that once extended from the Cape, through the Caribbean, South Atlantic, and to South Africa and the Indian Ocean. More...
  • Cape Canaveral LC17B Delta launch complex. Part of a dual launch pad complex built for the Thor ballistic missile program in 1956. Upgraded over the decades for use with Thor, Delta, Delta II, and Delta III launch vehicles, it remained in use for over half a century. More...

SCATHA Chronology


1979 January 30 - . 21:42 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17B. LV Family: Delta. Launch Vehicle: Delta 2914. LV Configuration: Delta 2914 629/D148.
  • SCATHA - . Payload: P 78-2. Mass: 360 kg (790 lb). Nation: USA. Agency: USAF. Class: Technology. Type: Communications technology satellite. Spacecraft: SCATHA. Completed Operations Date: 1991-05-28 . USAF Sat Cat: 11256 . COSPAR: 1979-007A. Apogee: 42,860 km (26,630 mi). Perigee: 28,018 km (17,409 mi). Inclination: 10.2000 deg. Period: 1,418.40 min. Spacecraft charging experiments. The SCATHA spacecraft had two charged particle injection systems, one of which was the Satellite Positive-Ion-Beam System (SPIBS). This was a xenon ion source which included some of the technologies used in thrusters: however, the discharge chamber was not performance optimized as was done with ion engines. Maximum operating power was 0.045 kW, and the ion source could produce a thrust of about 0.14 mN at a specific impulse of 350 s. Ions could be ejected at 1 keV or 2 keV. Neutralization was accomplished by a tantalum filament. The specific impulse was low because there was no attempt to optimize the propellant efficiency. The SPIBS system was ground-tested for a period of 600 hours. The SCATHA spacecraft was placed in a near geosynchronous orbit. Ion beam operations were performed intermittently over a 247 day period. The SCATHA flight demonstrated that a charged spacecraft, and the dielectric surfaces on it, could be safely discharged by emitting a very low energy (<50 eV) neutral plasma -- in effect shorting the spacecraft to the ambient plasma before dangerous charging levels could be reached. As of 28 August 2001 located at 153.98 deg W drifting at 4.513 deg E per day. As of 2007 Mar 8 located at 19.65W drifting at 4.513E degrees per day.

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