HALCA (Highly Advanced Laboratory for Communications and Astronomy), also known for its project nameVSOP (VLBI Space Observatory Programme), the code nameMUSES-B (for the second of theMu Space Engineering Spacecraft series), or justHaruka ("far away, distant" (はるか))[2] was a Japanese 8 meter diameterradio telescope satellite which was used forVery Long Baseline Interferometry (VLBI). It was the first such space-borne dedicated VLBI mission.
It was placed in a highly elliptical orbit with anapogee altitude of 21,400 km and aperigee 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 (u,v) 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 fromKagoshima 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.[3]
A follow-up missionASTRO-G (VSOP-2) 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 RussianSpektr-R mission as the only then operational space VLBI facility. Spektr-R stopped operating in 2019.
The large 8 meter antenna was designed to unfold in space as the unfolded configuration did not fit inside the rocket fairing. The antenna was a metal mesh of 6000 cables. To form an ideal shape the length of the cables were adjusted on the backside of the antenna. One concern was that the cables could entangle.[4] The deployment of the main reflector started on February 27, 1997. The deployment was done over three hours on the first day and was completed in 20 minutes during the next day.[5]
Payloads are separated by bullets ( · ), launches by pipes ( | ). Crewed flights are indicated inunderline. Uncatalogued launch failures are listed initalics. Payloads deployed from other spacecraft are denoted in (brackets).
