Cryocooler Applications

Space cryocoolers are miniature refrigerators designed to cool sensitive spacecraft components to cryogenic temperatures. NASA programs in Earth and space science observe a wide range of phenomena, from atmospheric physics and chemistry to stellar birth. Many of the instruments require low-temperature refrigeration to enable use of cryogenic detector technologies that increase sensitivity, improve dynamic range, or to extend wavelength coverage. The largest utilization of coolers is currently in Earth Science instruments operating at temperatures near the boiling point of liquid Nitrogen at 77 K (-321 degrees F). However, in support of studies of the origin of the universe and the search for planets around distant stars, interest has peaked in systems of low temperature refrigerators providing cooling down to 50 mK. This is just 0.05 degrees above absolute zero (-460 degrees F). NASA's development of a 20 K cryocooler for the European Planck spacecraft and its 2002 Advanced Cryocooler Technology Development Program (ACTDP) for 6-18 K coolers are examples of the thrusts to provide low temperature cooling for this class of missions. The major recent thrust toward low-temperature coolers has been with the development of the 6K cryocooler for theMIRI Instrument on the James Webb Space Telescope (JWST); it is scheduled for launch in 2018.

JPL Cryocooler Program Focus

Since the 1980s, JPL has had a strong interest in cryocoolers and has had a focused multi-year cryocooler development program. In the 1990s, the JPL cryocooler program included the procurement/development of pulse tube cryocoolers for the Atmospheric Infrared Sounder (AIRS) and Tropospheric Emission Spectrometer (TES) instruments, the conduct of extensive characterization testing of industry-developed cryocoolers, and the development and flight-testing of a wide variety of cryocooler integration technologies. Following those early activities, JPL focused on developing two 20 K sorption coolers for the Planck mission (launched in 2009) and on leading NASA's Advanced Cryocooler Technology Development Program (ACTDP) to develop 6 K cryocoolers for future NASA observatory missions, particularly the James Webb Space Telescope (JWST). Based on the TRW ACTDP cryocooler design concept, the 6K Mid Infrared Instrument (MIRI) cooler has been built and delivered by Northrop Grumman Aerospace Systems (NGAS) in Redondo Beach, CA, and is currently (2017) in final flight qualification testing at JPL. Other recent JPL cryocooler missions include the Orbiting Carbon Observatory (OCO-2) mission, which uses an NGAS HEC cooler, and the CheMin instrument on the Mars rover Curiosity, which landed on Mars in August 2012, and uses a Ricor K508 miniature Stirling cooler. To their credit, the coolers launched into space over the past several years are continuing to work flawlessly. For example, the AIRS instrument that was launched in May 2002, continues to operate 24/7 in orbit after 15 years.

Reviews of the overall JPL and NASA cryocooler programs are presented in the review papers at the head of the references section. Most of the cryocooler work at JPL has involved a combination of NASA and DoD sponsorship, and a close working relationship with the worldwide cryocooler development community. Links to the various JPL cryocooler activities are available through the above photo buttons and the entries on the left NavBar.

JPL Cryocooler Program Structure

The JPL cryocooler program has been focused in four areas:

1. The fundamental focus of the JPL cryocooler program is supporting the development and cryogenic engineering of JPL instruments that require cryocoolers to meet their scientific objectives. This activity involves cryogenic instrument design, cryocooler definition, selection and procurement, cryocooler integration engineering, and extensive cryogenic system testing. Several JPL flight instruments involving cryocoolers have been supported over the past 20 years. The largest are JPL's Atmospheric Infrared Sounder (AIRS) instrument, the Tropospheric Emission Spectrometer (TES) instrument, and the MIRI instrument.
2. To support the design of JPL's cryogenic instruments, a second principal focus has involved extensive characterization testing of industry-developed cryocoolers. This activity has been conducted to provide a thorough performance database for use by JPL and the broader NASA and DoD instrument development and cryocooler development communities. JPL initiated its cryocooler characterization program in support of the AIRS instrument in 1989, and greatly expanded the effort under the sponsorship of the Ballistic Missile Defense Organization (BMDO) and the Air Force Research Laboratory (AFRL) in 1992. Over the years 25 different cryocooler models have been characterized.
3. The third element of JPL's cryocooler program involves conducting research to develop cryocooler integration technologies needed to enhance the successful incorporation of cryocoolers into space instruments. Example cooler integration technologies include heat switches, heat interceptors, and closed-loop vibration suppression systems. A valuable part of this activity has been the conduct of selective flight experiments to provide flight heritage data and insure that no unresolved issues exist with respect to meeting the complete end-to-end development cycle of flight hardware.
4. A fourth element of JPL's cryocooler program (less active in recent years) has involved conducting research and development of advanced vibration-free sorption refrigerators for operation in the range of 10 to 25 K. An early accomplishment in this area was the development of JPL's Brilliant Eyes Ten-Kelvin Sorption Cryocooler Experiment (BETSCE), which was successfully operated aboard STS 66 in 1996. The most recent flight sorption cooler development was providing two flight 20 K sorption coolers for the Planck mission that launched in May 2009.