The Astrid-2 ground station in Solna outside Stockholm

Pictures from a visit on 23 March 2012

Sven Grahn

The ground station for Astrid-2 was established on the roof of the Swedish Space Corporation at Solna Strandväg 86, Solna, Sweden during 1998. Astrid-2 is the only satellite (so far) in the Swedish space programme that was not controlled from or used antennas at Esrange. Two important persons in this work were Klas Sjerling (RF systems) and Hans Ringstrand (computers, software and much else). The project manager for Astrid-2 was Staffan Persson. I was their boss as general manager of the Space Systems Division of SSC.

The station had an uplink to Astrid-2 on 2033.35 MHz which was frequency-shift keyed (FSK) and Bi-ø-L-coded. The data rate was 4.8 kbps. The station received data from the satellite on 2208.163 MHz which was BPSK-modulated and convolutionally encoded. The useful data rate was 128 kbps. The station block diagram is shown below.

The station was used during the period 10 December 1998 (the day of launch) - 24 July 1999 (loss of contact). The station was maintained about another year, but as the hope of another Astrid mission faded the station fell into a state of decay. Ventilation of the radome was maintained for another year or so. When I took these pictures on 23 March 2012 (about 13 years after launch) there was a left-over soldering station and several other tools and parts on the floor inside the radome. The radome is in surprisingly good condition but there is some moisture mold on the lower part of the inside of it. The equipment inside the radome show no signs of mold or corrosion and there are practically no cob webs. Only wooden parts show signs of decay.

Radome, antenna pedestal, rotor, antenna reflector and feed
were bought from Telonics near Phoenix, Arizona. A wide hole
was drilled through the concrete roof through which cables and ventilation air was run. The radom is made of very durable
plastic and the "triangles" are bolted together.

.
The small cowlings on each side of the entrance hatch are exits
for bathroom fans that sucked air from the building below and
blew it into the surrounding air. In this way the radome was kept
warm and dry even when wet snow fell on it.

The antenna reflector has a diameter of 1.7 meter (5.6 ft).
In the foreground you can see the counbterweights of the reflector.

The feed, inside the grey plastic can, is a three-turn helix.
The diplexer (blue) can be seen on the right.

The diplexer was made by Delta Microwave in US and the pre-amp/downconverter
(to 70 MHz) was made by Labetech in Sweden..

The power amplifier of the transmitter (with the two fans) was bought from the UK.

To save money we decided to avoid buying a stabilized high-power DC power supply for
the transmitter. Instead we used car lead-acid batteries (under the bench) and stan-
dard chargers (to the right of the bench) to replenish the batteries between satellite
passes.
The white box contains the exciter, i.e. the low-power part of the uplink transmitter. It
was modulated by the command signals from the control room. The exciter drove the
power stage of the transmitter (see above).

A view to the north-east. The full-scake mock-up of the Aries rocket can be seen.

View south. In the background are the grain silos of the now-defunct Pripps brewery.

The instrument rack one floor below the radome. Below the
computer screen is the drive unit for the antenna rotor. This unit
was fed signals from the (missing computer) which was fed orbital
elements from the control center computer four floors down in the
building. Below the drive unit is the PSK-modem (CM 701) from
Comstream. This odem was intended for geostationary satellites but
had had its software modified to handle the larger doppler shift
caused by the low orbit of Astrid-2.

Back to the Astrid-2 page

Radome, antenna pedestal, rotor, antenna reflector and feed were bought from Telonics near Phoenix, Arizona. A wide hole was drilled through the concrete roof through which cables and ventilation air was run. The radom is made of very durable plastic and the "triangles" are bolted together.	. The small cowlings on each side of the entrance hatch are exits for bathroom fans that sucked air from the building below and blew it into the surrounding air. In this way the radome was kept warm and dry even when wet snow fell on it.
The antenna reflector has a diameter of 1.7 meter (5.6 ft). In the foreground you can see the counbterweights of the reflector.	The feed, inside the grey plastic can, is a three-turn helix. The diplexer (blue) can be seen on the right.

The diplexer was made by Delta Microwave in US and the pre-amp/downconverter (to 70 MHz) was made by Labetech in Sweden..	The power amplifier of the transmitter (with the two fans) was bought from the UK.
To save money we decided to avoid buying a stabilized high-power DC power supply for the transmitter. Instead we used car lead-acid batteries (under the bench) and stan- dard chargers (to the right of the bench) to replenish the batteries between satellite passes.	The white box contains the exciter, i.e. the low-power part of the uplink transmitter. It was modulated by the command signals from the control room. The exciter drove the power stage of the transmitter (see above).
A view to the north-east. The full-scake mock-up of the Aries rocket can be seen.	View south. In the background are the grain silos of the now-defunct Pripps brewery.