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The Westerbork Array is an array of 14 radio telescopes with diameters of
25 metres each. The array is straight east-west with telescope zero (in
the west) through nine fixed, and telescopes A, B, C, and D moveable on a
railway track:
0 1 2 3 4 5 6 7 8 9 A B C D
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("=" is the railway). The fixed telescopes are 144 metres apart and the
maximum baseline length is 2.8km. Shadowing, which happens when one
telescope is in view of the next, occurs for sources near the celestial
equator, particularly for the shortest baseline (9A). The computer limits
elevations to above 5 degrees - below that you are probably observing
the trees anyway.
I think that's about enough technical stuff for now, except for this:
Around radio telescopes it is necessary to have disturbance-free zones.
The extremely weak radio signals are very vulnerable, so special care is
taken to remove all disturbances from the signal. A lot of disturbances are
prevented by not allowing any motorized vehicles near the telescopes. I
have seen numerous dick-heads who have, regardless of the warnings, driven
their cars into the area to have a short stroll through the neighbouring
park. This makes it necessary to throw away a lot of signal, screwing up
parts of someone's research and ruining many man-hours of work. How I hate
stupid people!
As it is forbidden for cars to enter the disturbance-free zone of
Westerbork, you have to park your car and then walk to the telescopes.
The state forest department has set out a special hiking trail from the
Hooghalen car park to the telescopes. Along the way there are educational
show-cases that tell a lot about a diversity of astronomical subjects.
Additionally, a scaled solar system can be observed along the same
track. This mainly tries to give you an idea of the relative sizes of the
planets and of the distances between them. Every step you take is 2.5
million kilometres in reality. The sun is as large as a football and the
planets have sizes ranging from centimetres to even millimetres. The whole
track is 4 kilometres long. Halfway there are also two parabolic
reflectors, which illustrate how radio astronomy uses dishes to collect
signals from far away. They are reasonably far apart, but when you whisper
at one end you can still be heard at the other. Finally at the end of the
path you reach the telescopes. There you will also find four show-cases,
giving some facts about about radio astronomy.
If you find yourself inside the Westerbork Observatory [1], one of the most
exciting things that can happen is the starting of an observation period.
The main thing that you can see happening is this: All 14 telescopes change
direction simultaneously. A majestic sight! After that the recording tapes
are changed and... you wait. And wait. (This is probably not one of the
best moments to try to explain the joys of being a radio astronomer.) What
I like about the institute is the small extension of the building which,
when standing inside, has the feel of an airport control tower. You feel you
control every movement of all the huge dishes. (I mean huge with comparison
to your average cereal plate.)
For most people in the Netherlands the name Westerbork rings quite a
different bell than it does for astronomers. During the second world war
there was a concentration camp at this same spot, where people had to wait
before being transported to the destruction camps in Germany. There is a
war memorial near the telescopes. An insane person once wanted to damage
the memorial, but because the people who take care of it are aware that
neo-nazis sometimes try to vandalize these kind of things, the memorial was
well protected. Frustrated, the man went to the Westerbork Array control
centre, which wasn't, and wrecked a lot of the computers. Everything is OK
again now, but alertness is now higher than it used to be.
How to get there: In Assen choose the road to Hooghalen, there turn right
across the railway tracks and then take the first road to the right. You
can also take the Hoogeveen-Assen train and depart at Beilen, take the road
to Hooghalen, there turn left across the railway tracks, etc.
It may be amusing to know the name of a small village nearby: Amen.
[1] http://www.nfra.nl/wsrt/index.htm
Attached documents:
Part of the Westerbork Array
