SSBUV (Shuttle Solar Backscatter Ultraviolet Spectrometer)

SSBUV is a NASA/GSFC instrument using UV backscatter observations in nadir to measure vertical profiles of ozone in the stratosphere and in the lower mesosphere in the spectral range from 200 to 405 nm. The objective is to fly the SSBUV payload on numerous Shuttle missions to provide complementary calibration data for long-term satellite ozone data sets. ^{1) 2) 3) 4) 5)}

The first flight with SSBUV instrumentation occurred on October 19, 1989 on the Shuttle Atlantis (STS-34). Throughout this Shuttle flight coincident observations were taken with the SBUV on Nimbus-7 and the SBUV/2 on NOAA-9 and NOAA-11 satellites.

Table 1: Survey of Shuttle flights with the SSBUV payload

The SSBUV instrument and its flight support electronics, power, data and command systems are mounted in the Shuttle's payload bay in two flight canisters (total mass of 410 kg). The SPAIM (Small Payload Accomodations Interface Module) interfaces SSBUV instrument to the Shuttle's avionic systems. The instrument canister holds the SSBUV instrument, its aspect sensors and inflight calibration system. Once in orbit, a motorized door assembly opens the canister, allowing the SSBUV to view the sun and the Earth. The canister closes, providing contamination protection, while SSBUV performs inflight calibrations.

The SSBUV instrument (PI: E. Hilsenrath) is in fact the SBUV/2 engineering model now flying on NOAA satellites (see POES series of NOAA). The SBUV/2 sensor is a spectrally scanning UV radiometer (nadir-viewing sensor) measuring solar irradiance and scene radiance (backscattered solar energy) over a spectral range from 200 to 405 nm (note: SSBUV actually measures from 160-405 nm; however, there is no calibration below 200 nm because a vacuum is needed for this region). Resolution = 50 km.

Table 2: Specification of the SSBUV instrument ⁶⁾

The SSBUV program has pursued a vigorous laboratory calibration effort using NIST- traceable standards. Of particular importance are the direct comparisons conducted with the instruments for the TOMS-EP (TOMS), ERS-2 (GOME), and NOAA-14 (SBUV/2) missions. These instruments were calibrated using SSBUV standards. The SSBUV flight on STS-72 provided a first opportunity to compare space observations from instruments which have been intercalibrated on the ground.

Figure 1: Illustration of the SBUV/2 instrument (image credit: NASA)

2) http://ssbuv.gsfc.nasa.gov/

3) http://ssbuv.gsfc.nasa.gov/fact_sheet.html

4) R. P. Cebula, E. Hilsenrath, P. W. DeCamp, K. Laamaan, S. Janz, K. McCullough, "The SSBUV Experiment Wavelength Scale and Stability: 1988 to 1994," Metrologia (Bureau International des Poids et Mesures), No 6, Vol. 32, Dec. 1995, pp. 633-636

5) http://www.gsfc.nasa.gov/gsfc/service/gallery/fact_sheets/earthsci/ssbuv.htm

6) Information provided by E. Hilsenrath of NASA/GSFC, Greenbelt, MD