COSMOCAL PROJECT
sunday - september 29 2024
fourth day of measurements:
- the first part of the slot was dedicated to the track scans of different orientations of the source's polarizer : the first round, we turned from 270º to 240º, with steps of 30º, then we did another round from 255º to 225º, again by steps of 30º, so in the end we sampled two periods every 15º
- in the second part of the slot (last 20 mins), we acquired a map of 5'x 5', centered in the new coordinates estimated by the alignement yesterday, with steps of 15 arcsecs and a scanning speed of 5 arcsec/s.
saturday - september 28 2024
third day of measurements:
- all observational time was dedicated to the alignement
- we run multiple ON scans, changing the azimuth and the elevation of the antenna, keeping the source fixed
- we estimated (through on-the-fly intensity polarization maps) that the best alignment is found when the antenna is set with offsets of -2' in Az and -15' in El
friday - september 27 2024
second day of measurements:
- acquired ON-OFF scans of the mm source
- we changed the polarizer's orientation by the following angles: 90º, 105º, 120º, 135º, 150º, 165º, 180º, 195º, 210º, 225º, 240º, 255º, 270º, 285º, 300º, 315º, 330º
- we acquired files to check the noise level of the mountain, the pws of the source with and without the chopper and finally with the hwp
- we had issues with the tuning: within every scan a tuning was done, so we observed a flat interval in the signal
thursday - september 26 2024
in the first day of measurements, we performed the following activities:
- with the source off, the hwp placed on the optical path but not spinning, we pointed the sky (close to the north pole) and then a source: on it we performed focus and pointing and applied corrections
- we moved to the mm source by running track command on pako, using the coordinates known from holography
- on the acquisition software, we looked for resonances and tuned them (with hwp still off); the saved parameter was already well adapted to the mountain load
- we started spinning the hwp at nominal 3Hz frequency
- we switched on the mm source along with the chopper, modulating at 1Hz
- at first, we saw no signal, but then we realised that the source's polarizer was set to 0º, hence minimising the signal, so we turned it to ~45º the signal appeared, with the correct hwp + chopper modulations
at this point, we started procedure to maximise the signal, by tilting the mm source in Az and El : here came some problems --> lost resonances, irregular signal (appearing and disappearing) and we could not go back to initial situation
- so we closed the vertex to see if the problem was in kids or in real signal, and we saw a constant signal of ~2kHz
- we opened the vertex again, tuned the resonances and the situation was quite stable again, so we took 3 ON-OFF scans