The Advanced Responsive Tactically-Effective Military Imaging Spectrometer (ARTEMIS) is
under development for tactical military applications and is the primary payload for the TacSat-3
satellite. The optical design for the telescope, imaging spectrometer, and high resolution imager is
An innovative cryocooler is under development that promises to provide high efficiency 4K-10K cooling for space-based focal plane arrays. It is based upon a novel modification of the Collins cycle, which is commonly used in large-scale high-efficiency terrestrial cryogenic machines. Cryogenic machines based on the conventional Collins or Brayton cycles routinely operate with input powers of about 740 Watts per Watt of refrigeration at 4K. Currently available
small-scale cryocoolers capable of about 1W of cooling at 4K typically require 5kW - 7.5kW per Watt of cooling. Microelectronic technology is employed in the modified cycle to enable a reduction in scale and mechanical complexity while retaining the high efficiency potential of the conventional Collins cycle. The modified Collins cycle is a continuous, or DC, flow device. This eliminates the need for the costly exotic alloys used in the regenerators of periodic, or AC, flow pulse-tube and Stirling type cryocoolers. It also permits separation of the cryocooler cold head from the load without a significant thermodynamic penalty, thereby enabling vibration isolation and the potential for improved system integration. An engineering prototype is currently undergoing development testing to demonstrate the potential of this concept to provide cooling at 10K and below. This paper will present the major design concepts employed in the engineering prototype, the results of initial engineering prototype development testing, as well as a discussion of the benefits of this approach and the anticipated space-based and terrestrial applications.
The Northrup Grumman Space Technologies High Efficiency Cryocooler (NGST HEC) was designed to support a 10 Watt cooling load at 95 Kelvin while rejecting heat to an effective sink interface temperature of 300 Kelvin. This design is an example of the pulse tube with inertance tube variant of the Stirling thermodynamic cycle whose compressor section uses dual opposed pistons to minimize vibration imparted to any cooling load through the cold end. The Air Force Research Laboratory has characterized the extended performance envelope of this refrigeration system, including its off nominal design point performance and efficiency, its response to transient loading and rejection temperatures, and its cool down performance from ambient. In order to assess this system's long term ability to support extended continuous duty space missions, this cryocooler has been running continuously for over two years, as part of a five year study on whether significant degradation in performance can be measured over that time. Finally, comparison of this cryocooler to other similar space qualifiable refrigeration systems has been made.
Air Force Research Laboratory’s space experiment XSS-10 was flown on the Air Force Global Positioning Satellite (GPS) mission IIR-8 launched on January 29, 2003. The mission objectives of XSS-10 were to demonstrate autonomous navigation, proximity operations, and inspection of a Resident Space Object (RSO). XSS-10 was a 28-kilogram micro-satellite was launched as a secondary mission on a Delta II expendable launch vehicle carrying a GPS satellite. XSS-10 was equipped with a visible camera, a star sensor, and mini SGLS system, all specially built for this program. In addition, a visible camera was attached to the second stage to observe the release of the micro-satellite and observe its maneuvers. Following the release of the GPS satellite, the Delta II initiated three depletion burns to reorient into an 800 KM circular orbit. The XSS-II was ejected from the Delta II second stage approximately 18 hours after launch. Operating autonomously on a preplanned course, XSS-10 performed its mission of navigating around the Delta II second stage at preplanned positions; the micro-satellite took images of the second stage and send them back to earth in real time. During these demonstrations the XSS-10 mission operations team accomplished responsive checkout of the micro-satellite and all of its subsystems, autonomous navigation on a preplanned course and a variety of algorithms and mission operations that pave the way for more ambitious missions in the future. This paper will discuss the results of the mission and post mission analysis of the XSS-10 space flight.
This paper presents an overview of the cryogenic refrigerator and cryogenic integration programs in development and characterization under the Cryogenic Technology Group, Space Vehicles Directorate of the Air Force Research Laboratory (AFRL). The vision statement for the group is to support the pace community as the center of excellence for developing and transitioning space cryogenic thermal management technologies. The primary customers for the AFRL cryogenic technology development programs are Ballistic Missile Defense Organization, the Air Force Space Based IR System Low program office, and other DoD space surveillance programs.