Catalogue source not working

[daniestevez]

I have noticed that the catalogue sources in ATA Track Scan are not working. For instance, when using casa as the source, I get

Press Enter to quit: /source got error: Command failed - Unable to lookup source casa - Source object lookup failed - PredictServer not ready/initialized
handler caught exception: Command failed - Unable to lookup source casa - Source object lookup failed - PredictServer not ready/initialized
Traceback (most recent call last):
 File "/home/destevez/.local/lib/python3.8/site-packages/ATATools/ata_rest.py", line 71, in _do_op
   raise ATARestException(json[cls.RETURN_MSG_KEY])
ATATools.ata_rest.ATARestException: Command failed - Unable to lookup source casa - Source object lookup failed - PredictServer not ready/initialized

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/home/destevez/gnuradio/gr38_uhd4/lib/python3/dist-packages/gnuradio/gr/gateway.py", line 78, in eval
   try: self._callback(arg)
 File "/home/destevez/gnuradio/gr38_uhd4/lib/python3/dist-packages/ata/control.py", line 142, in handle_msg
   self.point_src_id(self.obs_info['source_id'], self.my_ants)
 File "/home/destevez/gnuradio/gr38_uhd4/lib/python3/dist-packages/ata/control.py", line 265, in point_src_id
   src_ra, src_dec = ac.get_source_ra_dec(src_id)
 File "/home/destevez/.local/lib/python3.8/site-packages/ATATools/ata_control.py", line 170, in get_source_ra_dec
   source_data = ATARest.get(endpoint, json={'source': source})
 File "/home/destevez/.local/lib/python3.8/site-packages/ATATools/ata_rest.py", line 94, in get
   return cls._do_op(cls._OP_GET, endpoint, **kwargs)
 File "/home/destevez/.local/lib/python3.8/site-packages/ATATools/ata_rest.py", line 78, in _do_op
   raise ATARestException(str(e))
ATATools.ata_rest.ATARestException: Command failed - Unable to lookup source casa - Source object lookup failed - PredictServer not ready/initialized
^Cthread[thread-per-block[0]: <block ATA Control(3)>]: SWIG director method error. Error detected when calling 'feval_p.eval

Usually I'm using ac.track_source(antennas, source='casa') for catalogue pointing, but I think this doesn't support indicating an offset for on-off scanning.

[wfarah]

Hi @daniestevez. I haven't yet looked into this issue, but what I currently use for my observations is another function: ac.make_and_track_ephems. There's another procedure for on/off, but I think you've already used that?

[daniestevez]

@wfarah suggested using

az_offset = 20.
el_offset = 0.
ata_control.create_ephems2(source, az_offset, el_offset)
ata_control.point_ants2(source, "off", ant_list)
ata_control.point_ants2(source, "on", ant_list)

for on-off scanning. I have see that this is precisely what gr-ata does.

In fact the problem is not with the tracking itself, but rather with a call to ac.get_source_ra_dec(), which is only used to check if the source is up (if it isn't an error is printed instead of trying to track). I'm going to submit a PR that disables this call and assumes that the source is up as a quick way of getting this working.

I wonder if there is another way of getting the RADEC of catalogue sources. I would suggest astropy, but the names of the objects often don't match the names in the ATA catalogue.