The SORCE Mission – Going on Two Years
Gary Rottman [rottman@lasp.colorado.edu], Laboratory for Atmospheric and Space Physics, University of Colorado Boulder

SORCE was launched in January 2003 and has been functioning flawlessly since that time. The Orbital® spacecraft has met and exceeded all of our requirements and the four science instruments are providing excellent solar irradiance data. SORCE is the combination of two NASA missions: 1) our original SOLSTICE proposed in 1988 to be flown as part of the Earth Observing System (EOS); and 2) the Total Solar Irradiance Monitor, TSIM, proposal from LASP that NASA accepted in 1999. The required SORCE mission lifetime of eighteen months was surpassed this past July. The design lifetime is five years with a goal of six years, and we have every expectation that these milestones will also be successfully reached. In fact, there are no expendables within the spacecraft and instruments, and with the extensive redundancy it is reasonable to anticipate that all systems may continue to perform even well after 2008 — but with no guarantees. The TIM and SIM on SORCE are the prescribed instruments of the Total and Spectral Irradiance System, TSIS, on NPOESS with a first launch no earlier than 2012. This scenario indicates that there will more than likely be a gap between SORCE and NPOESS, and we are exploring possible options to insure data continuity. This presentation is an overview of the SORCE mission and will consider the future of total and spectral irradiance observations.