Mechanical cryocoolers represent a significant enabling technology for NASA's Earth and Space Science missions. An overview is presented of ongoing cryocooler activities within NASA in support of current flight projects, near-term flight instruments, and long-term technology development. NASA programs in Earth and space science observe a wide range of phenomena, from crop dynamics to stellar birth. Many of the instruments require cryogenic refrigeration to improve dynamic range, extend wavelength coverage, and enable the use of advanced detectors. Although, the largest utilization of coolers over the last decade has been for instruments operating at medium to high cryogenic temperatures (55 to 150 K), reflecting the relative maturity of the technology at these temperatures, important new developments are now focusing at the lower temperature range from 4 to 20 K in support of studies of the origin of the universe and the search for planets around distant stars. NASA's development of a 20K cryocooler for the European Planck spacecraft and its new Advanced Cryocooler Technology Development Program (ACTDP) for 6-18 K coolers are examples of the thrust to provide low temperature cooling for this class of missions. COOLERS ON NEAR-TERM EARTH AND SPACE SCIENCE MISSIONSIn spring 2002 three new cryocooler systems were launched into space to support NASA missions. Two of the three were based at least partially on the Oxford cooler technology that first flew on the Improved Stratospheric and Mesospheric Sounder (ISAMS) instrument in 1991; this type of cooler has demonstrated multi-year lifetime in orbit, and has been adopted by many long-life instruments to enable new and improved science. The third cooler, the NICMOS cooler, was the first space application of a long-life turbo-Brayton cooler.These recently launched coolers, which are reviewed below, have each now achieved over a year of successful operation in space, adding to the growing number of long-life space coolers enabling the acquisition of important new space-science data. These recent applications build upon the coolers of earlier NASA missions, such as those on the MOPITT, ASTER and Hyperion instruments that have achieved over two years of space operation at this point. 2 Additional coolers, such as the Northrup Grumman (TRW) pulse tube coolers on the TES instrument and the Ball Aerospace Stirling cooler on the HIRDLS instrument, are in the queue for launch aboard NASA missions in early 2004 and are also described below. RHESSI Gamma-Ray SpectrometerLaunched in February 2002, the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) uses an array of nine large germanium gamma-ray detectors to observe solar flares from 3 keV to 25 GeV. The detector

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Mechanical cryocoolers represent a significant enabling technology for NASA's Earth and Space Science missions. An overview is presented of ongoing cryocooler activities within NASA in support of current flight projects, near-term flight instruments, and long-term technology development. NASA programs in Earth and space science observe a wide range of phenomena, from crop dynamics to stellar birth. Many of the instruments require cryogenic refrigeration to improve dynamic range, extend wavelength coverage, and enable the use of advanced detectors. Although, the largest utilization of coolers over the last decade has been for instruments operating at medium to high cryogenic temperatures (55 to 150 K), reflecting the relative maturity of the technology at these temperatures, important new developments are now focusing at the lower temperature range from 4 to 20 K in support of studies of the origin of the universe and the search for planets around distant stars. NASA's development of a 20K cryocooler for the European Planck spacecraft and its new Advanced Cryocooler Technology Development Program (ACTDP) for 6-18 K coolers are examples of the thrust to provide low temperature cooling for this class of missions. COOLERS ON NEAR-TERM EARTH AND SPACE SCIENCE MISSIONSIn spring 2002 three new cryocooler systems were launched into space to support NASA missions. Two of the three were based at least partially on the Oxford cooler technology that first flew on the Improved Stratospheric and Mesospheric Sounder (ISAMS) instrument in 1991; this type of cooler has demonstrated multi-year lifetime in orbit, and has been adopted by many long-life instruments to enable new and improved science. The third cooler, the NICMOS cooler, was the first space application of a long-life turbo-Brayton cooler.These recently launched coolers, which are reviewed below, have each now achieved over a year of successful operation in space, adding to the growing number of long-life space coolers enabling the acquisition of important new space-science data. These recent applications build upon the coolers of earlier NASA missions, such as those on the MOPITT, ASTER and Hyperion instruments that have achieved over two years of space operation at this point. 2 Additional coolers, such as the Northrup Grumman (TRW) pulse tube coolers on the TES instrument and the Ball Aerospace Stirling cooler on the HIRDLS instrument, are in the queue for launch aboard NASA missions in early 2004 and are also described below. RHESSI Gamma-Ray SpectrometerLaunched in February 2002, the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) uses an array of nine large germanium gamma-ray detectors to observe solar flares from 3 keV to 25 GeV. The detector

The Alpha MagneticSpectrometer-02 (AMS-02) experiment is a state-of-the-art particle physics detector containing a large superfluid helium-cooled superconducting magnet. Highly sensitive detector plates inside the magnet measure a particle's speed, momentum, charge, and path. The AMS-02 experiment will study the properties and origin of cosmic particles and nuclei including antimatter and dark matter. AMS-02 will be installed on the International Space Station on Utilization Flight-4. The experiment will be run for at least three years.To extend the life of the stored cryogen and minimize temperature gradients around the magnet, four Stifling-cycle Sunpower M87N cryocoolers will be inte_ated with AMS-02. The cryocooler cold tip will be connected via a flexible strap to the outer vapor cooled shield of the dewar.Initial thermal analysis shows the lifetime of the experiment is increased by a factor of 2.8 with the use of the cryocooler.The AMS-02 project selected the Sunpower M87 cryocoolers and has asked NASA Goddard to qualify the cryocoolers for space flight use. This paper describes the interfaces with the cryocoolers and presents data collected during testing of the two engineering model cryocoolers.Tests include thermal performance characterization and launch vibration testing. Magnetic field compatibility testing will be presented in a separate paper at the conference.