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NASA Revamps Historic 4-Million-kg Mars Antenna
coondoggie writes NASA is working on some difficult renovations to reinvigorate its 70-meter-wide 'Mars antenna.' The antenna, a key cog in NASA's Deep Space Network, needs about $1.25M worth of what NASA calls major, delicate surgery. The revamp calls for lifting the antenna — about 4 million kilograms of finely tuned scientific instruments — to a height of about 5 millimeters so workers can replace the steel runner, walls and supporting grout."
Antenna problems are not specific to the iphone.
Might I suggest a crowbar. That's what I used for all my scientific research in Half Life. You could probably use one to lift the thing up a few millimeters.
Yes it's an anecdote! Were you expecting original research in a Slashdot comment?
So they're only revamping one out of three of the 70-m DSN antennae? I hope that they plan to do Canberra and Madrid, too. You need all three of them to get good 24-hr coverage. Actually, we need more of them. There are just too many missions needing 70-m time to downlink data right now. And nothing was sadder than watching good observations (which were otherwise totally possible) get killed because some other mission had priority on the big dishes.
We had to go through this with a 7 million kilogram antenna at the Green Bank Telescope:
http://www.gb.nrao.edu/gbt/track.shtml
The original azimuth track wore down too quickly, apparently due to faulty materials, workmanship, etc. You can see photos of the scope rotating out of the way sections of the track could be replaced at a time.
4 million kilograms; why can't we just use metric as it was intended?
4 Gigagrams.
This is not the first time that they have replaced the bearing on the 70 meter antennae. I believe that for DSS 14 (AKA Goldstone Mars) this would be the 3rd bearing change.
These 70 meters are reaching their end of life, and almost certainly will be replaced with arrays of smaller (but still large) antenna within the decade.
I work at a commercial communications satellite company and we have an old earth station with a 32 meter antenna that's rarely used today, but we still keep it as a backup. Actually, the cost of bringing it down is more than the scrap value, so it's mostly just standing there.
What nobody realized was that the antenna had been tracking a single geostationary satellite for decades, so it was moving very slightly around one position. Geostationary satellites aren't exactly stationary, but close, there's a slight movement around a central point.
The result was that, when they tried to point the antenna to a different satellite they found that the circular steel rail had been cold-rolled over the years so each wheel was sitting in a small valley in the rail. The azimuth motor didn't have enough torque to get off that valley and point the antenna to a different position, although there was no problem in tracking a satellite in the old position.
The solution was to jack up the whole antenna, cut off a section of rail and weld a new piece of rail beneath each wheel. The trickiest part was grinding the rail so that the new parts were perfectly aligned.