TABLE 3.3 Currently Funded Explorers

Program

Date Selected

Planned Launch Datea

Delta-Class Explorers

Extreme Ultraviolet Explorer (EUVE)

1982

1992

X-ray Timing Explorer (XTE)

1984

1996

Advanced Composition Explorer (ACE)

1989

1997

Far Ultraviolet Spectroscopy Explorer (FUSE)

1989

1999

Small Explorers (SMEX)

Submillimeter Wave Astronomy Satellite (SWAS)

1989

1995

a Launch dates after 1995 are uncertain.

observations in the 1- to 100-keV range with microsecond temporal resolution. XTE will advance our understanding of the physics of accretion flows around neutron stars and black holes, and of relativistic plasmas in the nuclei of active galaxies.

The Advanced Composition Explorer (ACE) will study the isotopic and elemental abundances of cosmic rays over a broad range of energies.

The Small Explorer program was initiated in the late 1980s to provide rapid access to space for payloads weighing less than about 200 kg. The stringent requirements of astronomy instruments often require pointing systems that weigh almost this amount by themselves; nevertheless, a number of imaginative proposals have been made. The Submillimeter Wave Astronomy Satellite has been selected as the first space mission to explore this wavelength band. As enhanced launch vehicles become available, a broader range of astronomical projects will become possible.

NASA is to be commended for its support of the analysis of data from the Infrared Astronomical Satellite (IRAS). The success of IRAS and of its General Investigator program serve as a model for the active support of Explorer missions. The committee urges NASA to provide strong support for the analysis of data from the Cosmic Background Explorer (COBE), including a vigorous guest investigator program.

The Suborbital Program

NASA's suborbital program trains students, tests instruments, and explores new scientific ideas by flying telescopes in rockets, balloons, and aircraft. This activity is NASA's only space science hardware program that operates on the time scale of a graduate student's career, allowing students and postdoctoral associates to be involved in all aspects of developing new instruments. Important



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