Solar occultation measurements during sunrises and sunset events at selected UV wavelengths were made during the UARS mission. Each event consisted of set of continuous UV irradiance measurements at a single wavelength that extended from an unbstructed view of the sun to complete occulation. Molecular oxygen occulations were gathered at 141, 160, and 171 nm. Each set of measurements were deconvolved and inverted using sophisticated algorithms to produce molecular oxygen density profiles in height ranges of 110-190 km in the thermosphere.
The profiles for over 1500 sunrise or sunset events are available via anonymous ftp. (Be sure to use "active" ftp mode for any transfers.) A more complete description of data and algorithms is given in Lumpe, et al., 2007. These molecular oxygen measurements were also the subject of an AGU poster presentation.
The seventh and perhaps final version (V22) of SUSIM solar UV irradiance data are now available from the SUSIM ftp site, "susim.nrl.navy.mil" in the subdirectory "[.uars.v22]". (Please note that one must use "active mode" in the ftp transfers.) These data extend from 12 October 1991 through 1 August 2005. Solar UV spectral irradiances are available on 4460 days which represents nearly 90% of the days during this period. The V22 reprocessing effectively begins at level 0, ends at level 3, and ranges over nearly all (except one) experiment days. Improvements were made in gain and temperature corrections, solar pointing corrections, lamp characterization, reference channel responsivities, and working channel responsivities especially at wavelengths above 260 nm.
Our sincere thanks go to all of the many many individuals and organizations who have contributed to the SUSIM program during both the 14 year flight history of the SUSIM UARS and also the previous 14 years of the SUSIM program.
The last solar UV spectral irradiance measurements of SUSIM UARS will be taken on 1 August 2005. Based on NASA Senior Review of ongoing Earth Science legacy missions, conducted earlier this year and recently released, the UARS Project was directed to discontinue the operations of SUSIM UARS. Although the report was very complementary of both SUSIM and UARS, the panel concluded that measurements provided by this aging platform are now redundant with newer experiments. We on the SUSIM Team plan to process all of the data, continue to publish our results, and participate in scientific meetings for as long as resources will allow.
More than two years ago, improvements in the SUSIM UARS calibration have significantly changed the measured Ly-α irradiance. The changes involved a fundamental reassessment of the degradation in the four onboard deuterium lamps. The resulting Ly-α irradiance time series (version V21r3) has been available in both ASCII and IDL save set formats on the SUSIM ftp site. A very brief readme file describes the data. This was announced earlier (see similar news item below). We reannounce because we are finding several users that are still unaware of the updated data.
A plot of the updated SUSIM Ly-α time series along with a comparison with that of SOLSTICE V18 can be viewed in the poster presentation given to the 2003 Fall AGU Meeting. Generally, this comparison shows an initial offset followed by some early relative variation followed by several years of nearly constant differences. Users of SUSIM Ly-α irradiance time series should definitely be using the updated V21r3 version.
The SUSIM website began 10 years ago. Much content has been added and we plan to continue to make improvements for the forseeable future. We hope that it serves the needs of the community.
Solar minimum spectra based on SUSIM data at 5 nm and 1 nm resolutions are now available for download. The corresponding submitted journal article is available as well.
SUSIM UARS continues to gather its daily scans whenever UARS power constraints will allow it or about 75% of days.
On 9 July 2003, SUSIM's last fresh MgF2 entrance filter was added to the working optical path that gathers the daily UV spectral irradiances. The instrument continues to acquire daily solar UV irradiance data as a part of the UARS traceability mission whenever spacecraft power is available (currently approximately 80% of all days). The goal of the UARS traceability mission is to take data coincident with newer satellite-based solar UV irradiance experiments, including those aboard TIMED, SCIAMACHY, SORCE, NOAA-16, and NOAA-17.
The latest version (V21r3) of the SUSIM UARS MgII core-to-wing ratio is now available. This version supercedes all previous versions.
A new Ly-a irradiance index (V21r3) is available from the SUSIM FTP site. This represents a substantial improvement over earlier versions especially during solar cycle 23.
SUSIM UARS UV irradiances are now available for days between October 12, 1991 and April 27, 2002 based on V21 processing. Still operating, SUSIM collects its 1.1 nm (mid) resolution solar scans from 115-410 nm each day as it has since it began operations on 11 October 1991. Irradiance data in the MgII (~280 nm) wavelength region are also collected daily using a different optical channel. Unfortunately in the last year, SUSIM experimental operations are periodically interrupted during UARS yaw-around maneuvers in order to conserve spacecraft power so that not all days are represented in the data set.
Because the CDHF was permanently shut down as of 30 November 2001, current day processing must be done using PACOR-A provided level 0 data on the SUSIM RAC.