Spitzer Documentation & Tools
Spitzer Telescope Handbook

Chapter 3. Observatory Description

The information in the next two chapters is gleaned from the Spitzer Observer’s Manual, the primary source of technical information for planning Spitzer observations during the prime (cryogenic) and warm missions.

3.1            Overview

Spitzer was launched from Cape Canaveral, Florida into an Earth-trailing heliocentric orbit on 25 August 2003. The observatory was launched with the telescope at ambient temperature; only the focal plane instruments were cooled to cryogenic temperatures. The telescope gradually cooled to ~30 K over a period of ~45 days.


Following launch, Spitzer entered a 63-day In-Orbit Checkout (IOC) phase, followed by a 35-day Science Verification (SV) phase, during which the planned capabilities of the telescope were verified, the detailed performance characterized, and the three science instruments and their operational modes commissioned.  Following the completion of IOC/SV, Spitzer was commissioned for routine cryogenic science operations on 1 December 2003. Only one science instrument can be on at any given time so observations were done in instrument campaigns ranging from ~ 7 – 21 days in length. The order of the campaigns during the prime (cryogenic) mission was IRAC – MIPS – IRS.


The prime mission continued until the exhaustion of the onboard cryogen used to cool the telescope and science instruments. The Spitzer cryogenic lifetime requirement was 2.5 years of normal operations, which was passed on 26 April 2006. Due to the excellent performance of the cryogenic system after launch and the implementation of warm and cold MIPS campaigns begun at the start of Cycle-3 (August 2006) to further extend the prime mission the revised estimated cryogenic lifetime was ~5.5 years.  The cryogen was depleted on 15 May 2009.


The first science observations during the prime mission included the First Look Survey (FLS), which was conducted by the SSC on behalf of the Spitzer observer community. The FLS was a ~110-hour survey using Director’s Discretionary Time. The goals of the FLS were to provide a characteristic first look at the mid-infrared sky and to rapidly process the data and place it in the public domain in time to impact early Spitzer investigations (specifically, Cycle-1 planning). The first science also included Guaranteed Time Observer (GTO) and Legacy Science observations. About 6 months after IOC/SV was completed, Cycle-1 General Observer (GO) observing commenced (June 2004). The majority of the original Legacy Science observations (the data of which were made public immediately) were completed within the first 18 months of the prime mission. The Spitzer Science Archive opened in May 2004, and initially contained FLS data, early release observations, and any Legacy data taken and reprocessed with the most current pipelines at that time.  Cycle-2 GO observations commenced in June 2005, Cycle-3 GO observations commenced in June 2006, Cycle-4 GO observations commenced in July 2007, Cycle-5 GO observations commenced in July 2008. The post-cryogenic (“warm”) mission got underway almost immediately after cryogen depletion on 15 May 2009, with a IRAC Warm Instrument Characterization (IWIC) phase, followed in July 2009 by the commencement of Cycle-6 science observations.