Encyclopedia Astronautica

American solar satellite. One launch, 1997.08.25.

The primary purpose of ACE was to determine and compare the isotopic and elemental composition of several distinct samples of matter, including the solar corona, the interplanetary medium, the local interstellar medium, and Galactic matter.

ACE was conceived at a meeting on June 19, 1983 at the University of Maryland. The meeting was hosted by George Gloecker and Glen Mason. The participants were Drs. L. F. Burlaga, S. M. Krimigis, R. A. Mewaldt, and E. C. Stone. This meeting had been preceded by preliminary documentation from the Johns Hopkins University Applied Physics Laboratory (APL) and the University of Maryland under the proposal name of Cosmic Composition Explorer. An unsolicited proposal was put together and forwarded to the NASA Explorer Program Office later that year, but was not acted upon.

The proposal was resurrected at the instigation of Dr. Vernon Jones and officially resubmitted to NASA in 1986 as part of the Explorer Concept Study Program. In 1988, the ACE mission was selected for a one-year "Phase A" (concept) Study. This study was a collaborative effort between spacecraft design and science teams.

The ACE Mission officially began on 22 April 1991 when the contract between NASA/GSFC and the California Institute of Technology was signed. APL, designer and builder of the ACE spacecraft, was involved in planning for Phase B (definition). The early ACE Spacecraft effort (April to July 1991) was primarily for ACE mission support, spacecraft system specification and ACE instrument support and interface definition. Phase B of the ACE mission officially began in August 1992.

The Mission Preliminary Design Review was held in November 1993. Phase C/D (implementation) began shortly thereafter.

Mission and Spacecraft Characteristics

The spacecraft was 1.6 meters across and 1 meter high, not including the four solar arrays and the magnetometer booms attached to two of the solar panels. At launch, it weighed 785 kg, which included 189 kg of hydrazine fuel for orbit insertion and maintenance. The solar arrays generated about 500 watts of power. The spacecraft spun at 5 rpm, with the spin axis generally pointed along the Earth-sun line and most of the scientific instruments on the top (sunward) deck. In order to get away from the effects of the Earth's magnetic field, the ACE spacecraft traveled almost 1.5 million km from the Earth to the Earth-sun libation point (L1). By orbiting the L1 point, ACE stayed in a relatively constant position with respect to the Earth as the Earth revolved around the sun. Science Goals The primary purpose of ACE was to determine and compare the isotopic and elemental composition of several distinct samples of matter, including the solar corona, the interplanetary medium, the local interstellar medium, and Galactic matter. The nine scientific instruments on ACE performed:

  • Comprehensive and coordinated composition determinations
    • Elemental
    • Isotopic
    • Ionic charge state

  • Observations spanning broad dynamic range
    • Solar wind to galactic cosmic ray energies
    • (~100 eV/nucleon to ~500 MeV/nucleon)
    • Hydrogen to Zinc (Z = 1 to 30)
    • Solar active and solar quiet periods

  • Investigations of the origin and evolution of solar and galactic matter
    • Elemental and isotopic composition of matter
    • Origin of the elements and subsequent evolutionary processing
    • Particle acceleration and transport in nature


Electric System: 0.50 average kW.

AKA: Advanced Composition Explorer.
Gross mass: 785 kg (1,730 lb).
Unfuelled mass: 596 kg (1,313 lb).
Height: 1.00 m (3.20 ft).
First Launch: 1997.08.25.
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 2 7000 American orbital launch vehicle. The Delta 7000 series used GEM-40 strap-ons with the Extra Extended Long Tank core, further upgraded with the RS-27A engine. More...
  • Delta 7920-8 American orbital launch vehicle. Three stage vehicle consisting of 9 x GEM-40 + 1 x EELT Thor/RS-27A + 1 x Delta K with 2.4 m (8 foot) diameter fairing) More...

Associated Manufacturers and Agencies
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • APL American manufacturer of rockets and spacecraft. Applied Physics Laboratory, Johns Hopkins University, Laurel, MD, Laurel, Maryland, USA. More...

  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • NASA Report, ACE Brochure, Web Address when accessed: here.
  • NASA Report, ACE Mission Paper, Web Address when accessed: here.
  • NASA Report, ACE Spacecraft, Web Address when accessed: here.
  • NASA Report, Position and Orientation of subsystems on the ACE spacecraft , 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 LC17A Delta launch complex. Part of a dual launch pad complex built for the Thor ballistic missile program in 1956. Pad 17A supported Thor, Delta, and Delta II launches into the 21st Century. More...

ACE Chronology

1997 August 25 - . 14:39 GMT - . Launch Site: Cape Canaveral. Launch Complex: Cape Canaveral LC17A. LV Family: Delta. Launch Vehicle: Delta 7920-8. LV Configuration: Delta 7920-8 D247.
  • ACE - . Payload: ACE. Nation: USA. Agency: NASA Greenbelt. Manufacturer: APL. Class: Earth. Type: Magnetosphere satellite. Spacecraft: ACE. USAF Sat Cat: 24912 . COSPAR: 1997-045A. Apogee: 128,196 km (79,657 mi). Perigee: 176 km (109 mi). Period: 86,411.37 min. Summary: Earth-Sun L1 point.

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