This paper describes the design, development, testing and performance at Ball Aerospace of long life, 4-10 K temperature space cryocoolers. For temperatures down to 10 K, Ball has developed long life Stirling cycle cryocoolers. For temperatures to 4 K and below, Ball has developed a hybrid Stirling/J-T (Joule-Thomson) cooler. The hybrid cooler has been verified in test to 3.5 K on a Ball program and a 6 K Development Model is in development on the NASA/JPL ACTDP (Advanced Cryocooler Technology Development Program). The Ball ACTDP cooler Development Model will be tested in 2005. The ACTDP cooler provides simultaneous cooling at 6 K (typically, for either doped Si detectors or as a sub-Kelvin precooler) and 18 K (typically, for optics or shielding) with cooling stages also available at 40 and 180 K (typically, for thermal shields or other components). The ACTDP cooler is under development for the NASA JWST (James Webb Space Telescope), TPF (Terrestrial Planet Finder), and Con-X (Constellation X-Ray) missions. The 4-10 K Coolers are highly leveraged off previous Ball space coolers including multiple life test and flight units.
The Atmospheric Infrared Sounder (AIRS) is one instrument in a suite of six instruments currently flying onboard NASA’s Earth Observing System (EOS) Aqua spacecraft. NASA’s Aqua spacecraft was launched successfully on May 4, 2002 from Vandenberg Air Force Base in California. AIRS is a cryogenic instrument developed under a Jet Propulsion Laboratory contract by BAe Systems formely Lockheed Martin Infrared Imaging Systems, for NASA. AIRS will provide new and more accurate data about the atmosphere, land and oceans, which provides a powerful new tool for climate studies and enables the advancement of weather prediction models. AIRS observations permit the measurement of the atmospheric temperature with an accuracy of 1 K in 1 km thick-layers in the troposphere and surface temperatures with an accuracy of 0.5 K. The Aqua spacecraft was placed in a sun-synchronous near-circular polar orbit with an inclination of 98.2 degrees, mean altitude of 705 km, 98.72 minute orbit period and 1:30 pm ascending node. The nominal on-orbit mission lifetime for the instrument is 6 years. AIRS measurements are based on passive infrared remote sensing using a precisely calibrated, high spectral resolution grating spectrometer with an infrared coverage from 3.7 to 15.4 μm. To achieve this high performance over this broad wavelength range, the spectrometer is cooled to 155 K and the Mercury Cadmium Telluride (HgCdTe) focal plane is cooled to 58 K. The detectors are cooled by a pair of long-life, low vibration, pulse tube mechanical coolers to 58 K, and a two-stage passive cooler with a deployable Earth shield provides cooling for the spectrometer to achieve a stable temperature near 155 K. This paper provides a general overview of the cryogenic system design and presents its on-orbit performance for the first year of operation.
Mechanical cryocoolers represent a significant enabling technology for precision space instruments by providing cryogenic temperatures for sensitive infrared, gamma-ray, and x-ray detectors. However, the vibration generated by the cryocooler's refrigeration compressor has long been identified as a critical integration issue. The key sensitivity is the extent to which the cooler's vibration harmonics excite spacecraft resonances and prevent on-board sensors from
achieving their operational goals with respect to resolution and pointing accuracy. To reduce the cryocooler's vibration signature to acceptable levels, a variety of active vibration suppression technologies have been developed and implemented over the past 15 years. At this point, nearly all space cryocoolers have active vibration suppression systems built into their drive electronics that reduce the peak unbalanced forces to less than 1% of their original levels. Typical systems of today individually control the vibration in each of the cryocoolers lowest drive harmonics, with some
controlling as many as 16 harmonics.
A second vibration issue associated with cryocoolers is surviving launch. Here the same pistons and coldfingers that generate vibration during operation are often the most critical elements in terms of surviving high input acceleration levels. Since electrical power is generally not available during launch, passive vibration suppression technologies have been developed. Common vibration damping techniques include electrodynamic braking via shorted motor coils and the use of particle dampers on sensitive cryogenic elements.
This paper provides an overview of the vibration characteristics of typical linear-drive space cryocoolers, outlines their history of development, and presents typical performance of the various active and passive vibration suppression systems being used.
Mechanical cryocoolers represent a significant enabling technology for NASA's Earth and Space Science Enterprises. Over the years, NASA has developed new cryocooler technologies for a wide variety of space missions. Recent achievements include the NCS, AIRS, TES and HIRDLS cryocoolers, and miniature pulse tube coolers at TRW and Lockheed Martin. The largest technology push within NASA right now is in the temperature range of 4 to 10 K. Missions such as the Next Generation Space Telescope (NGST) and Terrestrial Planet Finder (TPF) plan to use infrared detectors operating between 6-8 K, typically arsenic-doped silicon arrays, with IR telescopes from 3 to 6 meters in diameter. Similarly, Constellation-X plans to use X-ray microcalorimeters operating at 50 mK and will require ~6 K cooling to precool its multistage 50 mK magnetic refrigerator. To address cryocooler development for these next-generation missions, NASA has initiated a program referred to as the Advanced Cryocooler Technology Development Program (ACTDP). This paper presents an overview of the ACTDP program including programmatic objectives and timelines, and conceptual details of the cooler concepts under development.
The atmospheric infrared sounder (AIRS) is being developed for the NASA Earth Observing System (EOS) program with a scheduled launch on the first post meridian (PM-1) platform in the year 2000. AIRS is designed to provide both new and more accurate data about the atmosphere, land and oceans for application to climate studies and weather prediction. Among the important parameters to be derived from AIRS observations are atmospheric temperature profiles with an average accuracy of 1 K in 1 kilometer (km) layers in the troposphere and surface temperatures with an average accuracy of 0.5 K. The AIRS measurement technique is based on very sensitive passive infrared remote sensing using a precisely calibrated, high spectral resolution grating spectrometer operating in the 3.7 micrometer - 15.4 micrometer region. The instrument utilizes a cryogenically cooled infrared spectrometer that uses a pair of pulse tube cryocoolers operating at 55 K to cool the HgCdTe focal plane detectors to 58 K. The instrument also has cryoradiators operating at 190 K and 150 K to cool the spectrometers' optical bench to 155 K. The cryocooler system is a highly integrated part of the AIRS instrument development whose design is focused to maximize the overall performance of the instrument. This paper provides a brief description of the AIRS instrument design and focuses on the results achieved to date on the development and integration of the pulse tube cryocoolers into this demanding instrument. In particular, the paper describes the cooler cryogenic and the overall thermal performance of the cryocooler. The thermal characteristics of the cooler system with the cold link coupling assembly also are presented.