NASA Revamps Historic 4-Million-kg Mars Antenna 66
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."
Re:4 million kilograms (Score:1, Informative)
Ahem [wikipedia.org]...
_AC
Not the first time (Score:4, Informative)
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.
Re:We had to do this with a 7 million kg antenna (Score:3, Informative)
You use a track on the GBT, but the 70 meters use a large horizontal bearing. These are Apollo era antennae, old enough that they were originally pointed with a internal ha-dec antenna model as an analogue computer (as was the old 140 foot at Greenbank). They really need to be replaced.
Happened where I work (Score:5, Informative)
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.