Spacelab-2 Plasma Depletion Experiments for Ionospheric and Radio Astronomical Studies
M. MENDILLO 1,
J. BAUMGARDNER 1,
D. P. ALLEN 1,
J. FOSTER 2,
J. HOLT 2,
G. R.A. ELLIS 3,
A. KLEKOCIUK 3, and
G. REBER 3
1 Department of Astronomy, Boston University, Boston, MA 02215.
2 Massachusetts Institute of Technology, Haystack Observatory, Westford, MA 01886.
3 Department of Physics, University of Tasmania, Hobart, Tasmania, Australia.
The Spacelab-2 Plasma Depletion Experiments were a series of studies to examine shuttle-induced perturbations in the ionosphere and their application to ground-based radio astronomy. The space shuttle Challenger fired its orbital maneuvering subsystem engines on 30 July and 5 August 1985, releasing large amounts of exhaust molecules (water, hydrogen, and carbon dioxide) that caused the electrons and ions in Earth's upper atmosphere to chemically recombine, thereby creating so-called "ionospheric holes." Two burns conducted over New England produced ionospheric peak depletions ranging from 25 to 50 percent, affected the ionosphere over a 200-kilometer altitude range, and covered 1° to 2° of latitude. Optical emissions associated with the hole spanned an area of several hundred thousand square kilometers. A third burn was conducted over a low-frequency radio observatory in Hobart, Australia, to create an "artificial window" for ground-based observations at frequencies normally below the natural ionospheric cutoff (penetration) frequency. The Hobart experiment succeeded in making high-resolution observations at 1.7 megahertz through the induced ionospheric hole.
Submitted on May 26, 1987
Accepted on September 22, 1987
