title: Satellite-borne limb scanning UV spectrometer for thermospheric remote sensing.
abstract: A concave grating Wadsworth spectrometer designed to scan the UV limb of the earth was flown on a Defense Department meteorological satellite to obtain measurements of atmospheric emissions in the 85-395-nm wavelength range as a function of height above the solid earth. The instrument field of view was 0.14 x 3.8 degrees corresponding to 6 km in the vertical and 230 km in the horizontal at the limb. The scanning motion was controlled by a momentum compensated dc-torque motor mechanism that panned the line of sight across the limb corresponding to tangent altitudes of 80-480 km. A set of three photon counting detectors, each viewing a separate exit slit, provided simultaneous coverage of the wavelength bands of 85-120 nm (EUV), 110-163 nm (far UV), and 290-395 nm (UV) at a wavelength resolution of 0.4, 0.8, and 1.2 nm, respectively. A separate photometric channel isolated the atmospheric sodium doublet at 589.0-589.6 nm. The grating position and instrument view angle were controlled by digital circuitry operating on hardwired and uplinked command instructions. The operating modes included a variety of scanning and fixed wavelength and view angle operations. A description of the instrument and several examples of the data are presented. These include the dayglow emissions from thermospheric oxygen and nitrogen that form the basis of a thermospheric density determination, auroral enhancements observed in these emissions and in hydrogen Ly-alpha, and nighttime sodium emissions.
authors.affiliation: Aerospace Corporation, Space Sciences Laboratory, P.O. Box 92957, Los Angeles, California 90009, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Pranke
authors.forename: A B
authors.initials: AB
authors.lastname: Christensen
authors.forename: F A
authors.initials: FA
authors.lastname: Morse
authors.forename: D R
authors.initials: DR
authors.lastname: Hickman
authors.forename: W T
authors.initials: WT
authors.lastname: Chater
authors.forename: C K
authors.initials: CK
authors.lastname: Howey
authors.forename: D A
authors.initials: DA
authors.lastname: Jones