26m Pointing Solutions

This notes were ported from the auscope wiki 1.0 - Updated for new procedures.

This page describes work to use the PCFS on hobart and the Hobart 12m DBBC to measure pointing and gain characteristics of the 26m.

Setting up

Use the PCFS version that uses dbbchb in DDC mode and mk5hb

hobart: fs-auscope

Starting the observations.

Check that the sources you want to observe are not commented out. Edit /usr2/control/ctlpo.ctl if necessary. Then:


Data will be logged to /usr2/log/sx.log

Stoping the observations

In the field system:


Then zero out the offsets:


Understanding the solutions

Search the RA wiki for Bricky

See also:

newsmerd: ~/Brucehack.sh

To mount image of 26m antenna control floppy:

mount -o loop sys26m.june2017.img /mnt/usb/

Useful pages

Observing log

2017 18 - 23 Oct: Observing three sources around Dec = -42 to look for repeatability of pointing over full elevation range, get idea of variation in gain.

2017 23 Oct - : Paused for Callisto noise diode monitoring

2018 23 - 24 Feb : All-sky survey. Lots of non-detections, presumably due to poor weather. Cloud, rain. Data may not be much use for gain curve measurement. Stopped at 055/00:20 UT due to poor weather.

2018 25 Feb : 056/2240 UT : started observations again in good weather. Much tweaking of source list and got working by 057/0305 (26 Feb) UT. ~10:00 UT: Simon takes over for VLBI NAPA

26 Feb ~21:00 UT: Re-started pointing but SX looks to be warm. Asked Brett to investigate. 058/10:38 : Stopped.

67/22:30 UT: Started in good weather following fix of hydraulics fault. Stopped by Simon at ~68/02:00 UT

79/01:40 UT: More pointing. Wind close to limbs, partly cloudy.

2018/106 (16 Apr) 04:20 UT: Started pointing with new model loaded following Y-encoder replacement. X solutions should be OK but Y may not be. There is a -0.07 deg DC offset plus the solutions acquired with the old Y encoder. These observations are for testing/verification of the new model but a subsequent update is required probably. Weather is windy at start, partly cloudy.

2018/107 (17 Apr) 01:40 UT: Re-started with pointing model after previous one discovered to have offsets applied with the wrong sign (oops). Good weather.

2018/129 (9 May): The previous pointing model was made with the wrong sys26m configuration file. It was set so that the correction file for the old encoder (SN 6007) was in use rather than the new one. The current Y1 encoder has an unknown serial number but by process of elimination is probably 6106. The host.cfg file on sys26m has now been changed accordingly. The current pointing model in XY_GRID.BIN is the model used for the old Y1 encoder (6007) but with a -0.07 deg offset determined by Jamie (newsmerd:~observer/floppyimage/XY_GRID_20180412.BIN). Pointing will be done with this setup, currently on sys26m, but awaiting good weather. High winds and rain forecast for the next few days…

2018/129 (9 May): The above assumption appears to be incorrect. The pointing offsets I’m getting in Y are varying on the same source with every scan, indicating a big oscillation. We are back to using a model that includes corrections for the oscillation in the gridded model and the wrong encoder model. The sys26m boot floppy is labeled: <WRAP center round box 60%> sys26m 1/5/18
Y model oscillation
Jim Lovell
Y oscillation in grid model
sys26m.01May2018.img </WRAP>

2018/145-148 : Low winds, clear skies, so running some gain/pointing observations with the gridded oscillation model above

2018/148 (28 May). I've constructed a model for the current “mystery” encoder on Y1 that has the previously used wrong model subtracted and the new oscillation added. The encoder file is called mystenc01.bin. This is being used together with XY_GRID_20180412.BIN as the gridded model (see above for a description). The sys26m boot floppy is labeled: <WRAP center round box 60%> sys26m 28/5/18
Y1 encoder model for
mystery encoder
Old pointing model + DC offset
sys26m.20180528.img </WRAP>

2018/148/0220 : Pointing run started

2018/148/0400 : Results on TauA show big oscillation. Reverting to sys26m.01May2018.img which includes oscillation in gridded model, while I try to work out what's going on.

2018/149 (29 May): Analysis shows wrong signs in encoder model file. New floppy ready to go: <WRAP center round box 60%> sys26m 29/5/18
Y1 encoder model for
mystery encoder
Old pointing model + DC offset
sys26m.20180529.img </WRAP>

2018/149/2300 : Pointing observations with new config started - Jim Lovell

2018/151/2249 : Another new encoder model being trialed. sys26m.20180530.img - Disk label: <WRAP center round box 60%> sys26m 30/5/18
Y1 encoder model for
mystery encoder
Old pointing model + DC offset
sys26m.20180530.img </WRAP>

2018/151 - 2018/154 : pointing observations with the new configuration resulting in a new gridded model XY_GRID_20180604.BIN. Now loaded in sys26m from disk image newsmerd:~observer/floppyimage/sys26m.20180604.img. Disk label: <WRAP center round box 60%> sys26m.20180604,img
New Y1 enc model: 00000003.bin
New gridded pointing model: 20180604
Jim Lovell
4/6/18 </WRAP>

2018/175.23:20 : Pointing verification tests started