Summary of the SπRALS telecon, April 8

Hardware

Warkworth and Ceduna receivers

Cooled (50K), 3-7 GHz, linear receivers. They are being developed by Ray, work can go ahead even in lockdown. Sergei: can the range be increased to 2-9 GHz? Are there feedhorn limits? Send current performance specs of amplifiers and rx of Wa and Cd to Ray. Another hardware issue: how to observe two frequencies at once at these telescopes?

Yarragadee upgrade

Probably not May, Gabor will follow up on this.

Software

PCONV: converting polarizations to a common basis

PCONV will be an AIPS task Mark is writing, that will deal with the linear and circular polarization conversion issues for our astrometry in a simplified way. Mark is now testing it on s001c data. Seems to work so far, some AIPS issues remain. add pdf file from Mark and more description

Procedures and Tests

How many maser can be shared in a track?

Lucas tested by flagging every other scan in MultiView test data (his PhD data). The astrometric repeatability went from 30-40 uas (unflagged), to 70-100 uas. Will test some more, but initial observations won't be shared track.

How many ring QSOs are optimal: 4, 5 or 6?

Start with 6-7 in first epoch of the initial experiment and see if they can be reduced (depends a lot on calibrator quality). Each ring cycle should be as short as possible to better sample ionospheric structure. Upper limit is in the 10-20 min range. add more to this from Richard's email

What are the top maser and QSOs for first parallaxes? Are we missing QSOs?

Nine sources selected for initial measurements based on compactness (how good is the maser for measuring a parallax) and calibrator availability. An additional source is also targeted that has a parallax from BeSSeL, to test and compare results. Haven't yet checked the missing QSO problem in the calibrator survey. add the initial target list from the text file

Do we have station locations to less than 1cm accuracy?

Do this in C-band instead due to rx limitations at the moment. Wa had a local tie survey (tying to position to Ww 12m) and a few geo-VLBI sessions in the recent years. How accurate is the position? (Cd is only about 2-3 cm, the rest of UTAScope is probably better. Gabor will look this up.)

We will do this experiment after the initial parallax experiments finished (12-hr solid geoblock observations in C-band, probably more than one epoch). Also, what was the issue with the KVN station position being not that good for a long time? add comments from Sergei, Richard, others

Start a parallax sequence for 1 or 2 masers, continue G232 maser sequence

These will be scheduled over the next few weeks. Will focus on:

 # G323.740-0.263: bright, compact, good looking calibrator distribution
 # G287.371+0.644: good LST range that can be observed with others in a single long experiment without sharing a track.
 # G232.620+0.996: Already did an epoch back in september and π peaks is now. Used to test and compare to BeSSeL.

Although G323 and G287 are far from parallax optimums (which will be in June-August), they are good for the first observation to test logistics.

Test using wide C-band geoblock setup

For example 256 MHz each at 3.3 and 6.7 GHz. Will do this in the near future on Hb-Ke single baseline. Cd possibility of doing multiple frequencies at once? (see HW section)