|
Solar radio astronomy at Metsähovi
The Metsähovi Radio Observatory, a separate research institute of the
Helsinki University of Technology since May 1988, operates a 14 m diameter
radio telescope at Metsähovi, Kylmälä,
24o 23' 38''E, 60o 13' 05''N
elevation 60 m. The Cassegrain telescope system can
be used at frequencies 10-100 GHz (wavelengths 3 cm - 3 mm). Part of the
telescope observing time has been used for solar research since 1976.
Solar mapping with mini-computer based recordings started in 1978.
Annually the telescope has been reserved for solar measurements for 4-10 weeks,
typically during summer months. Measurements include maps of the whole or part
of the Sun, tracking of active regions and solar oscillation monitoring. Most
of the solar observations have been done using receivers operating at 22.2
GHz or at 36.8 GHz. The sensitivity of the receivers is good enough for 0.1 sfu
resolution. In the temperature scale the resolution is better than 100 K and
it is limited by short term changes in the atmospheric attenuation.
Solar maps are measured by scanning the solar disk in right ascension and by
changing the declination in small steps between the subsequent scans (an
example of a map here).
Tracking of an active region is done by pointing the beam of the telescope
to the area in question and then by taking samples at a selected rate, usually
10-20 samples per second (an example of a track plot
here). The output of the receiver is connected to an
A/D-converter. The digitalized data is stored on a MicroVAX II computer and
is later processed and calibrated for graphic presentation.
A list of solar reports is also available. For any further questions or comments see our addresses at contact information page.
|
