astronomy

HALCA

HALCA is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand HALCA rather than just read about it. In short: HALCA (Highly Advanced Laboratory for Communications and Astronomy), also known for its project name VSOP (VLBI Space Observatory Programme), the code name MUSES-B (for the second of the Mu Space Engineering Spacecraft series), or just Haruka ("far away, distant" (はるか)) was a Japanese 8 meter diameter radio telescope satellite which was used for Very Long Baseline Interferometry (VLBI). It was the first such space-b…

Key takeaways

HALCA belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HALCA to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HALCA from memory before moving on to harder problems.

Reference excerpt

HALCA (Highly Advanced Laboratory for Communications and Astronomy), also known for its project name VSOP (VLBI Space Observatory Programme), the code name MUSES-B (for the second of the Mu Space Engineering Spacecraft series), or just Haruka ("far away, distant" (はるか)) was a Japanese 8 meter diameter radio telescope satellite which was used for Very Long Baseline Interferometry (VLBI). 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 (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 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 (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 Russian Spektr-R mission as the only then operational space VLBI facility. Spektr-R stopped operating in 2019.

Antenna 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. 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.

Highlights Observations of hydroxyl masers and pulsars at 1.6 GHz Detection of interference fringes for quasar PKS1519-273 between HALCA and terrestrial radio telescopes Routines imaging of quasars and radio galaxies etc. by means of experimental VLBI observations with HALCA and terrestrial radio telescope networks

Gallery

References

External links

HALCA VSOP Archived 2021-03-21 at the Wayback Machine

Illustrations

Worked examples

Example 1 — a first encounter with HALCA

Start with the simplest possible case. Write down what HALCA claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to HALCA before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about HALCA ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of HALCA

In research: HALCA appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses HALCA in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: HALCA is common in secondary-school and first-year university syllabi. It links to neighbouring topics Radio telescopes, Satellites of Japan, Space telescopes, so understanding it makes those chapters shorter.
In everyday life: Look for HALCA outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study HALCA in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HALCA means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain HALCA out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HALCA in simple terms?

Why does HALCA matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study HALCA?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on HALCA.