GBT OPERATIONS PROCEDURES

Number: 853-04

Title: 85-3 Snow Stow

Last Revision: 28 MAR 03

General

Remember to keep 85-3 in mind when snow, ice, or freezing rain may be a problem. 85-3 should be stowed anytime the above precip starts to stick to metal surfaces, after you have parked the GBT, and assuming winds are not a problem. High winds take precedence over snow. If winds are expected to be greater than 35mph, the antenna should be stowed to zenith instead per stowing for high wind instructions.

 

To stow 85-3 for snow:

STEP

ACTION

1

Enter the gbiop password to unlock the screen saver on Marsha (Linux machine in USNO control room closest to the door to the server room).

2

Click on the "Halt" button on the T85_3 window.

A popup window should appear asking "Do you really want to perform a halt".

3

Click on "yes".

4

Click on the Obs Mode "Halt" button and select "Snow 1" OR "Snow 2" from the drop-down menu basing your decision on the current wind direction. 

"Snow 1" will park the antenna facing the NorthEast.
"Snow 2" will park the antenna facing SoutheEast. 

You should choose the postion that will closest place the wind hitting the dish from the edge or at some angle from the back-side.

5

The antenna should slew to commanded snow position based on your choice above and the brakes should set (indicated by the red highlighted Brakes "On" for each axis). 

Note that unlike the GBT, it will not travel at a reduced rate. It will slew until it is near the postion, then slow down and settle in on the commanded position. There is no stow pin to insert.

6

Click on the lock picture on the status bar at bottom right corner of the screen to lockout the terminal.

7

Make note of the time you halted observing on the 85-3 paper log in the "<O>ther" section and charge it as lost time due to weather. The Logbook is kept on the desk beside osiris. Also add an info. comment in the GBT OPSLOG program that you halted observing on 85-3.

8

Make note of the shutdown on the Operator's white board in the GBT control room if still offline at the end of your shift.
9

Wait until weather conditions are favorable before putting the antenna back on line per 85-3 Startup instructions.
NOTE: If you have been shut down for an extended period of time and temperatures have fallen or if you suspect a large buildup of snow or ice on the structure, leave the antenna offline and contact Pete.

10

Log the re-start time on the paper log and in the GBT OPSLOG program.

Info:

If you have any concerns about when or where to park the antenna or when to resume operations, or if you have any problems stopping or re-starting, call Pete.

 

Prepared By: Pete Chestnut

Last modified: 11 NOV 02