Transit Inclinometry

Since this task is often done remotely from Hilo during the day it will be described here as if always done remotely. The safety issues encountered during remote operations are of paramount importance. Please ensure you have read the safety protocols and comply with them.

Contents

• Rationale
• Monitoring
• Description of Test
• Safety Issues & Who should read these instructions
• Handover of responsibility within JCMT
• Co-ordination of tasks
• Task Commands
• Shutdown
• Data processing
• Updating the archive
• The archive

The Monitoring Phase
It is imperative that a regular (weekly) check be done in order to establish the cause of recent changes in the amplitude of this characteristic, and to mitigate against subsequent changes in pointing behaviour once the cause is identified.

General description of test
A new inclinometer has been mounted on the TMU where the old UKT14 mirror used to be. The telescope is to be tipped over to about 10 degrees and the TMU tilted correspondingly so that the inclinometer is horizontal. A fictitious source is tracked through transit. This track must be

• long enough to simulate the defects of hysteresis and friction exactly as seen during astronomical tracking
• short enough to make for a quick test
• short enough to minimize the range of elevations encountered by the inclinometer so that it stays within its operating range of +200".

Safety
If the measurements are to be made remotely, you should review the safety protocols before proceeding. These instructions are for

• The TSS who may be leaving the telescope ready for remote command
• The JCMT Workleader who must coordinate any remote work
• The person in Hilo acquiring the data, if being done remotely.

Handover from normal nighttime operations

• The TSS should leave the telescope drives ON.
• The antenna could be sent to the zenith at azimuth=178 for convenience.
• The summit telescope software should be run down.
• The TSS should tell the person in Hilo that setup is complete.
• Display 'Inclinometry in progress' sandwich board at foot of stairs to left nasmyth.

Coordination and Initiation of Activities

• Read the safety protocols !! Thank you.

Commands

• Run up inclinometry software, and include tmu_load after incline_load.
• Check position of TMU with
  • send tmu get x_pos         ( or y_pos )
• Adjust the position of the TMU :
  • obeyw tmu move_to 19594   1066
  • (changed from 19639 , 980 on 20020314)
  • (changed from 19594 , 1063 on 20020906)
• Adjust the elevation of the antenna using incline_centre :
  Send it first to (RA,DEC) = (LST + 00:15:00, -60:10:00) RD.
• For other settings, the relationship between DEC and y_pos giving a zero inclinometer reading may be

  DEC = 19.8258 + y_pos/100 - 90 - 0.0574 degrees (needs confirming)

• RECORD THIS DECLINATION FOR LATER USE IN THE REDUCTION.

• Take inclinometry samples using send incline obey log test 1.
  Stop data collection by send incline cancel log.
  Display data by $ ty/page test.log.
  Each line shows the azimuth and 14 channels of data.
  The signal from 'TMU_Y' is the 2nd channel of data.
  
• Adjust elevation until the TMU_Y signal is +1000 (mV).
  The TMU-Y signal will become more negative as the antenna rises.
  The inclinometer scale is ~20.8mV/arcsec.
• NB : Do not attempt to adjust the position of the TMU using explicit TMU commands : such commands force the TMU to return to y_pos = 0 as part of the adjustment - you don't want that to happen.
• Check that the azimuth is still approximately 178.5^o.
  If it is significantly different from 178.5^o, then adjust the (RA,DEC) accordingly :
  if it is <178^o, for instance, then set the RA to LST + 00:14:00.
• Collect data by allowing the log command to keep running. You can give this command a special output filename rather than the dummyname 'test'.
• Note the starting azimuth.
• Wait about 30 minutes.
• Do send incline cancel log when the azimuth is as much beyond 180^o as it was before 180^o at the start.

• Read the safety protocols
• Run down remote inclinometry software.

Data processing

Updating the archive

The archive