KFPA Astrid Pointing Modes

Modification Request #? (C04 2009)


1. Introduction

Effective use of the KFPA requires regular peaking on a bright radio source and and adjusting the sub-reflector position to focus the telescope. The Astrid procedures used perform these tasks must be updated. This MR concerns extension of the existing Astrid point and focus modes to explicitly allow the observer to select the SIGNAL and REFERENCE beams. This extension requires Astrid to develop a model for the angular locations of all beams.

Our planed approach, for the near term, is to update the dual beam procedures for the KFPA use, by allowing the observer to explicitly select SIGNAL and REFERENCE beams. Later MRs will request more optimum use of the KFPA array for pointing and focus observations.

2. Background

We have described KPFA pointing and focus plans for commissioning previously. The document describes re-configuration of the existing Astrid procedures and a new pointing mode to allow checking the relative gain of the 7 feeds.

3. Requirements

Astrid shall command pointing and focus observations with observer specified signal and reference beams. The Peak and Focus procedures requiring updates are:

For brevity, we describe these procedures collectively as Peak and Focus observations.

4. Design

A standard set of optional parameters should be added to all astrid procedures concerned with pointing and focus. The parameters are the indexes to the beams to be used for different rolls in the peak and focus process. Since future procedures will allow different combinations of beams for different functions, below we suggest a general syntax for specifing all beams used in a particular process.

  • SIG=I, where I is index to one of beams in the array (range 1 to N) (ie SIG=1)
  • SIG=I,J,K,L, where I,J,K,L are indicies to beams in the array (ie SIG=1,2,3,4)
  • SIG=ALL, where ALL indicates all beams should be configured for the observations
  • REF=M, where M is the index of another of the beams for sky subtraction (ie REF=2)
  • REF=OTHERS, where OTHERS indicates all beams not in the SIG list.

For Peak and Focus, the initial requirements are only to supply single beams for signal and reference. Initially, the KFPA Peak and Focus algorithms will be identical to those used for the current K band, dual beam receiver. That is, the system will center the point and focus observations on the Signal beam and subtract the reference beam intensity, as an estimate of system and sky temperature. The Astrid analysis code must compute/fit the expected signal contributions due to the source occasionally being present in the REF beam during Peak observations, as is currently done.

The Peak and Focus observations can be made more efficient by use of several beams for estimation of the REF signals. The REF signal could be the average (or better median) of the OTHER beams, for a better estimate of the off source system temperature. The options needed for spectral line mapping, SIG=ALL, REF=OTHERS, etc, are not used, but are noted for completeness. The spectral line mapping routines will require specification of SIG beams, if the observer will configure the spectrometer for multiple spectral bands.

The SIG and REF parameters are optional. The default values for SIG are the center beam (feed 1) and the beam due east of that beam (feed 2) (East defined when the telescope is at azimuth = 0, due North).

5. Example Usage

#Astrid Script to point and focus the telescope before a spectral line observation.
#HISTORY
#09AUG19 GIL Revised as an example for MR
#09FEB01 GIL KFPA single pixel tests

#First put in your sources
execfile("/home/astro-util/projects/TKFPA/sources.cat")

#!!!!!!!!!!!!!!!!! be sure that this is the correct setup !!!!!!!
Configure("""/home/astro-util/projects/TKFPA/configK0_19.py""")
SetValues( "LO1",{"restFrequency":21000.})

sourceName="3c123"
Slew(sourceName)
Balance()

Peak(sourceName                                   #source name
   , Offset("Encoder", "00:12:00", 0)             #offset Az
   , Offset("Encoder", 0,          "00:12:00")    #offset El
   , 30                                           #time
   , SIG=1                                        #signal beam
   , REF=2)                                       #reference beam

#note that future versions c
Slew(sourceName)
Focus(sourceName,-120.0, 240.0, 60.0   # object, start, length in mm, time
   , SIG=2                                        #signal beam
   , REF=5)                                       #reference beam

Example of new sequence of calls to the revised Peak and Focus routines.

6. Deployment Checklist

Steps in the deployment checklist.

7. Test Plan

7.1 Internal Testing

The software group must fill out this section This section covers things like unit testing, simulator testing, and any other tests required to make sure this MR is ready for sponsor/integration/regression testing.

7.2 Sponsor Testing

The sponsor testing for these procedures will be repeated execution of the modified procedures, listed above, for three types of radio of sources, bright, moderate and weak intensities. These test observations will be carried out in modest weather conditions, (neither perfectly clear nor rainy). Predicted zenith atmospheric tau should be in the range .05 to .1 The sponsor testing will include making peak observations with each beam of the array selected as the SIG beam and also each beam of the array selected as REF beam (but not all combinations (only 7 tests, not 7*6/2 = 21 peaks per source type).

7.3 Integration/Regression Tests

What do the integration/regression testers need to do in order to test this MR. Software Group will add this section

Signatures

APPROVED To the best of my knowledge, the request in this MR is complete. I have thought through this request, and believe it to be an important feature to implement or bug to fix.
ACCEPTED I acknowledge that I have validated the completed code according to the acceptance tests.

Written DONE - Glen Langston - 2009 August 19
Checked ALERT! - name - date
Approved by Sponsor ALERT! - name - date
Approved by CCC ALERT! - name - date
Accepted/Delivered by Sponsor ALERT! - name - date

Symbols: Use %X% if MR is not complete (will display ALERT!) Use %Y% if MR is complete (will display DONE)

CCC Discussion Area--

-- GlenLangston - 2009-08-19
Topic attachments
I Attachment Action Size Date Who Comment
kfpa7Use09May18.pdfpdf kfpa7Use09May18.pdf manage 415 K 2009-08-19 - 10:32 GlenLangston KFPA point/focus/pipeline
Topic revision: r2 - 2009-08-19, GlenLangston
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