The X-band Haystack Long Range Imaging Radar (LRIR) is currently undergoing an upgrade that will add a W-Band (92-100 GHZ) imaging capability for satellites in low earth orbits. The upgraded system will be known as the Haystack Ultrawideband Satellite Imaging Radar (HUSIR). The W-band capability will provide a bandwidth of 8 GHz, eight times greater than the previous X-band capability, and is expected to be operational in 2013. The previous X-band capability, which provided an imaging resolution of about 25 cm out to geosynchronous orbit, will be retained and is expected to be back in operation in 2012.
Installation of the new Haystack antenna (photograph from Lincoln Laboratory 2011 Annual Report, p. 27).
Previously Proposed Upgrades
A 1993 paper discussed a potential W-Band upgrade to the Haystack radar. The objective of the proposed upgrade was to achieve a sensitivity comparable to the existing X-Band Haystack LRIR but with a bandwidth of 8 GHz and a resolution of 3 cm. This paper stated the goals for the amplifier of the proposed upgrade were a peak power of 100 kW, an average power of 30 kW, with pulse lengths of between 30 μs and 1.0 ms and a maximum duty cycle of 30%. The proposal required a new antenna, which was estimated to provide a gain of 84 dB. It was estimated that under favorable viewing conditions (normal winter atmosphere with clouds, 60˚ elevation angle, a single 100 μs pulse would provide a sensitivity S = 51.8 dB (1 m2 target, range of 1,000 km). This is very similar to the current sensitivity of the X-band LRIR, suggesting that the W-band radar might also be capable of imaging out to geosynchronous orbit altitudes. However, unlike the X-band radar, the W-band radar was very sensitive to moisture in the atmosphere.
A 2001 Naval Research Laboratory report stated that to meet Space Command requirements, the Air Force had proposed an 8 GHz bandwidth Haystack upgrade that would have a peak power > 5 kW and a duty cycle of 20%. This upgrade was described as enabling the imaging of the “increasing number of orbiting micro-satellites.”
The W-Band Upgrade
There appear to be relatively few technical details about the HUSIR upgrade publicly available. The new W-band capability will operate between 92 and 100 GHz, with a bandwidth of 8 GHz. Although there do not appear to be any official claims about resolution, it has been repeatedly described as providing almost a factor of ten improvement, which would indicate a resolution as low as about 3 centimeters.
The replacement of Haystack’s existing antenna with a new one with the same 36.6 m diameter but with finer tolerances began in 2010. Installation and initial alignment of the new antenna was completed in 2011. The new antenna has a surface tolerance of 100 μm (600 μm in the old antenna) and has higher angular motion speeds of 5 degrees/second in azimuth and 2 degrees/second in elevation (2 degrees and 1.5 degrees per second, respectively for the old antenna).
 Lee B. Spence and Richard J. Tempkin, “A Very High Power, Wide Bandwidth Imaging Radar Design,” 1993 IEEE National Radar Conference, pp. 182-185.
 A table in the paper indicated that the radar would have a capability against “high altitude satellites with integration.” Spence and Tempkin, “A Very High Power,” p. 185.
 G. M. Borsuk, Robert Kemerley, Bruce Wallace, Bobby Junker, Max Yoder, “DoD Investment Strategy for Vacuum Electronics R&D and Investment Balance for RF Vacuum Electronics and Solid State R&D,” Naval Research Laboratory NRL/MR/6800–01-8570, April 8, 2001. Available at: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA393327.
 Kevin Gilmartin, “Major upgrade to Haystack radar will enable enhanced imaging of space,” Press Release, Hanscom Air Force Base, May 19, 2010.
 Lincoln Laboratory, 2011 Annual Report, p. 27. Available at: http://www.ll.mit.edu/publications/MITLL_2011_annual_report.pdf.
 MIT Lincoln Laboratory, 2010 Annual Report, p. 12. Available at: http://www.ll.mit.edu/publications/Annual_Report_2010.pdf.