The Upper Atmosphere Research Satellite (UARS) is ending its mission in 2005 after almost 14 years in orbit. All but one of the UARS instruments, including LASP’s SOLSTICE instrument, were officially turned off Monday, August 1. The satellite was launched on the space shuttle on September 12, 1991. “The mission has been extremely successful and LASP should be proud of constructing an instrument capable of such a long lifetime and for providing a calibrated data product over these many years,” according to Charles Jackman, UARS Project Science Office, NASA. The mission’s objective is to study the Earth’s chemistry, dynamics, and energy balance above the troposphere, and the UARS mission is probably best known for its program to study global ozone change.

The NASA Senior Review recommended that the UARS satellite should be supported until January 2006, with only the UARS HALOE (Halogen Occultation Experiment) making observations until the very end. UARS has 10 instruments on-board, and five were still taking measurements after 5073 days in orbit— SOLSTICE, HALOE, SUSIM, PEM, and HRDI. With a battery cell reversal in battery pack #2 on August 22, UARS is now crawling along with just one battery pack, and plans to de-orbit UARS are being accelerated to this October. Because UARS does not have enough propulsion left to completely dump UARS into an ocean, UARS will be placed into an elliptical orbit so that it will re-enter in about 2 years.

SOLSTICE (Solar Stellar Irradiance Comparison Experiment) was built at LASP, with Gary Rottman leading the team. It has been taking measurements of the solar ultraviolet irradiance from 119 to 420 nm. These solar UV irradiance measurements are also being made from the SORCE satellite since 2003, and SORCE is expected to continue this long-term data set for several more years. The combination of overlapping missions permits the study of long-term solar irradiance variations as shown in the figure of the bright hydrogen emission at 121.6 nm. In addition to routine solar measurements, UARS SOLSTICE has also been used to make lunar, planetary (e.g., comets), and atmospheric absorption (solar occultation) observations.

Hydrogen Emission (121.6 nm)

The success of the UARS SOLSTICE is due largely to the dedication of many staff members at LASP and UARS project members at GSFC since 1978 (even before today’s CU students were born), so many thanks to all of those who contributed to this outstanding UARS mission and the resulting long-term data set.