HALCA


HALCA, also known for its project name VSOP, the code name MUSES-B, or just Haruka was a Japanese 8 meter diameter radio telescope satellite which was used for Very Long Baseline Interferometry. It was the first such space-borne dedicated VLBI mission.

History

It was placed in a highly elliptical orbit with an apogee altitude of 21,400 km and a perigee altitude of 560 km, with an orbital period of approximately 6.3 hours. This orbit allowed imaging of celestial radio sources by the satellite in conjunction with an array of ground-based radio telescopes, such that both good plane coverage and very high resolution were obtained.
Although designed to observe in three frequency bands: 1.6 GHz, 5.0 GHz, and 22 GHz, it was found that the sensitivity of the 22 GHz band had severely degraded after orbital deployment, probably caused by vibrational deformation of the dish shape at launch, thus limiting observations to the 1.6 GHz and 5.0 GHz bands.
HALCA was launched in February 1997 from Kagoshima Space Center, and made its final VSOP observations in October 2003, far exceeding its 3-year predicted lifespan, before the loss of attitude control. All operations were officially ended in November 2005.
A follow-up mission ASTRO-G was planned, with a proposed launch date of 2012, but the project was eventually cancelled in 2011 due to increasing costs and the difficulties of achieving its science goals. It was expected to achieve resolutions up to ten times higher and up to ten times greater sensitivity than its predecessor HALCA.
The cancellation of ASTRO-G left the Russian Spektr-R mission as the only then operational space VLBI facility.

Antenna

The large 8 meter antenna required to be unfold in space, as it did not fit unfolded in the rocket fairing. The antenna was a metal mesh, consisting out of 6000 cables. To form an ideal shape the cables required to have an ideal length. For this purpose the length of the cables were adjusted on the backside of the antenna. One concern was that the cables could entangle. The deployment of the main reflector started on February 27, 1997. The deployment did take three hours on the first day and was completed at the next day in 20 minutes.

Highlights