Solar Spectral Flux Radiometer, SSFR


Research Staff: Warren Gore, Peter Pilewskie, and Larry Pezzolo

In early 2000, the Ames Atmospheric Radiation Group completed the design and development of an all new Solar Spectral Flux Radiometer (SSFR, see Figure 1). The SSFR is used to measure solar spectral irradiance at moderate resolution to determine the radiative effect of clouds, aerosols, and gases on climate, and also to infer the physical properties of aerosols and clouds. The newest version of the SSFR was designed primarily for airborne platforms and thus it has no moving parts. Two instruments were built and successfully deployed in three field missions: 1) the Department of Energy Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE) II in February/March, 2000; 2) the Puerto Rico Dust Experiment (PRIDE) in July, 2000; and 3) the South African Regional Science Initiative (SAFARI) in August/September, 2000. Additionally, the SSFR was used to acquire water vapor spectra using the Ames 25-meter base-path multiple-reflection absorption cell in a laboratory experiment.

[SSFR Block Diagram]
[SSFR Image]

The SSFR (Figure 2) spectral range is 300nm to 1700nm with 8-12nm resolution. It has zenith- and nadir-viewing hemispherical field-of-view light collectors. The signal is transmitted by high-grade optical fibers to the rack-mounted instrument system. The heart of the instrument is the monolithic diode array spectrometer-pair (visible and near-infrared) employed for each viewing direction (zenith and nadir). Light at the entrance slit is dispersed by a concave imaging grating onto a diode array (Si or InGaAs) producing a complete spectrum within a fraction of a second. The output is then processed by dedicated electronics. The data acquisition and control system is a 266 MHz Pentium-class embedded controller in a PC104 format. Data are recorded on a compact 220 Mbytes PCMCIA flash memory card. The visible spectrometer is temperature regulated by a heater control circuit while the InGaAs detector array is cooled by a thermo-electric cooler for optimum performance.

The NASA Ames SSFR specifications are:

The compact design of the new Solar Spectral Flux Radiometer has facilitated its integration on many current airborne platforms including the NASA ER-2, the University of Washington CV-580, the Department of Energy Twin Otter, the Space and Naval Warfare Systems Command (SPAWAR) Navajo, the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter, and the General Atomics Altus Uninhabited Aerial Vehicle.

Collaborator: John Pommier, Bay Area Environmental Research Institute


Point of Contact: Warren Gore, 650/604-5533,