Participate in DMSP SSUSI calibration/validation (cal/val) programs
for currently flying satellites (F16-18)

ars_thumbThe Special Sensor Ultraviolet Spectrographic Imager (SSUSI) has a spectrograph and imaging mode. In its imaging mode, SSUSI measures emission across the disk within the following bands: Ly α [119 -124 nm], 130.4 [128-132 nm], 135.6 [134-137 nm], N2 Lyman Birge Hopfield LBHS [140-152 nm], and LBHL [165-180 nm]. CPI's attention has been directed to disk imaging data in four of these five spectral channels (the exception being 130.4). The along-track and cross-track dimensions of SSUSI images are provided by orbital motion and a cross-track scanning mirror with a period of 22 s. The figure below shows examples of LBHL and Ly α images of the auroral oval at northern latitudes during an active period.

CPI's involvement with SSUSI goes back to the 1990s as the lead algorithm developer for deriving data products from dayglow and auroral imaging data, and as a key Applied Physics Laboratory (APL) team member in designing and developing ground-processing operational software. Dayside data products include O/N2 (column density ratio serving as a signature to negative ionospheric storms), QEUV (integrated measure of solar EUV energy flux shortward of 45 nm) and their use in estimating NmF2 (peak electron density in F2-layer) and HmF2 (altitude of peak). Use is made of data from the 135.6 and LBHS spectral channels. Auroral products include parameters describing electron and proton precipitation, NmE (peak electron density in auroral E-layer), and HmE (altitude of peak). Use is made of data from the LBHS, LBHL, and Ly α channels. The dayside algorithms make use of extensive outputs from CPI's AURIC model. In turn, the auroral algorithms make use of extensive outputs from CPI's B3C model. Both are well documented in peer-reviewed papers.

CPI has been an active participant in each of the SSUSI cal/val programs (starting with the launches of F16 (in 2004), F17 (in 2006) and F18 (in 2009)). Work has been focused in three areas: calibration, validation of dayside products, and validation of auroral products. Our calibration efforts have been directed to comparisons of SSUSI dayside data with TIMED/GUVI data and with radiances from AURIC. For F18, CPI has also taken the lead on comparisons with coincident Special Sensor Ultraviolet Limb Imager (SSULI) data (by the companion FUV sensor of the Naval Research Laboratory). Validation of dayside products has focused on comparisons of QEUV with independent solar measurements and of NmF2 and HmF2 with ground-based ionosonde data. Auroral validation efforts have been directed to comparisons of precipitation products (average energy Eavg and energy flux Q) with coincident data from SSJ/5 (on-board electron and proton particle sensors) and comparisons of NmE and HmE with incoherent scatter radar data. Knight et al. [J. Geophys. Res., 2008] provide a detailed description of our SSUSI-SSJ/5 work.

SSUSI F16 auroral images for two of the three spectral channels used to specify precipitation characteristics (the third channel is LBHS, shortward of the LBHL channel). Contours of constant solar zenith angle at 90° and 100° are displayed to identify nightside versus dayside observations.

More details on the modeling capabilities can be found in the AURIC brochure.