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Analysis of Q Band On-sky recommissioning data

After the successful lab tests (QBandLabTests), on October 20, 2006 the refurbished Q band receiver was installed on the GBT. This page presents the results of the on-sky recommissioning tests.

The project file for each night of commissioning

• TQ_01: The first commissioning observations were made on Nov. 14, 2006. While pointing and focus were okay, no other useful data was acquired. This is probably due to condensation of water on the dewar window. Note that the R1 and R2 cables were reversed for these observations. This was fixed the next day.

• TQ_17NOV06 and TQ_18NOV06: The weather was excellent this night--cold and clear. Unfortunately, there was definitely water on the dewar window. We (Gary, Ron, and D.J.) confirmed this by going up to the top of the receiver room at 2am, removing the radome and wiping the water off with a paper towel. We got maybe and hour or two of useful data before more water recondensed on the window. Subsequent to this observing run, Gary installed a valve on the radome to purge it with warm, dry nitrogen. They replaced the saturated dessicant packs in the radome as well. This appears to have fixed the problem.

• TQ_05DEC06: After two previous attempts to get data with the Q band receiver thwarted by water on the dewar window, we had a successful set of observations this night. The windy conditions prevented us from making band-scan to measure T(sys), but the pointing scans suggested a T(sys) of about 80 K around 40 GHz. We were, however, able to make a number of astronomical observations of fairly bright sources. Spectra for these observations, after calibration, but without baseline removal, are attached below
  • We started by observing W3(OH) using an OffOn procedure, with the Off position 1 degree away and changing positions every 2 minutes at the frequencies of H52 alpha and H53 alpha (scans 54-59). Both recomb lines were easily detected in a 2 minute scan. With a deeper integration, we also saw the associated recomb lines from Helium, and a number of molecular lines: HCCN, 29SiO, and HCS+. Note that the second beam was on blank sky for these observations. The baselines for these data have some structure, probably due to the bright continuum background.
  • We also observed the SiO maser using a Nod procedure switching beams every 2 min from the Mira variable OH 141.7+3.5 (scans 65-78), and easily detected both the v=1 and v=0 lines of the J=1-0 transition. These spectra, lacking a bright continuum background, have perfectly flat baselines. The v=0 data have been Hanning smoothed to show the line.
  • We finished up spending the last 2 hours tracking the North Celestial Pole (scans 79-138). These data are also attached below. The final spectra were reduced as if we had been Nodding the telescope. The waterfall plots for the NCP scans are also attached. For the waterfall plots, we have removed a 0th order baseline and spaced each spectrum by 3x the noise in the first spectrum. These plots show that there are still occasional scans with ringing, particularly in the L polarization (this may be due to something in the Optical Drivers, however). This contrasts with the final lab tests with ambient loads that showed no sign of ringing.

• TQ_12DEC06: T(sys) measurements were made this night. They have been attached below. The receiver works from 38.2-49.8 GHz, with T(sys) values of about 50-150 K depending on the frequency (worse at high frequencies) and channel (feed 0 is slightly worse than feed 1). The atmospheric T(sys) ranged from 30-120 K and opacity ranged from 0.067 - 0.3 from 38 GHz to 50 GHz, so conditions were median or better for these observations. T(cal) values ranged from about 5-10 K; plots of T(cal) are attached below as well.

-- DjPisano - 29 Aug 2007

Attachment:	Action:	Size:	Date:	Who:	Comment:
W3OH_L_IF1_F1.ps	action	56485	06 Dec 2006 - 16:51	DjPisano
W3OH_L_IF1_F2.ps	action	58556	06 Dec 2006 - 16:52	DjPisano
W3OH_L_IF2_F1.ps	action	57437	06 Dec 2006 - 16:52	DjPisano
W3OH_L_IF2_F2.ps	action	57067	06 Dec 2006 - 16:52	DjPisano
W3OH_R_IF1_F1.ps	action	56954	06 Dec 2006 - 16:54	DjPisano
W3OH_R_IF1_F2.ps	action	59560	06 Dec 2006 - 16:54	DjPisano
W3OH_R_IF2_F1.ps	action	56551	06 Dec 2006 - 16:55	DjPisano
W3OH_R_IF2_F2.ps	action	60413	06 Dec 2006 - 16:55	DjPisano
OH141.73.5_L_IF1.ps	action	300844	06 Dec 2006 - 16:55	DjPisano
OH141.73.5_L_IF2.ps	action	63716	06 Dec 2006 - 16:55	DjPisano
OH141.73.5_R_IF1.ps	action	304219	06 Dec 2006 - 16:55	DjPisano
OH141.73.5_R_IF2.ps	action	64389	06 Dec 2006 - 16:56	DjPisano
NCP_IF0_PL0.ps	action	61793	06 Dec 2006 - 16:56	DjPisano	L pol
NCP_IF0_PL1.ps	action	61967	06 Dec 2006 - 16:56	DjPisano	R pol
NCP_IF1_PL0.ps	action	58361	06 Dec 2006 - 16:56	DjPisano	L pol
NCP_IF1_PL1.ps	action	59115	06 Dec 2006 - 16:58	DjPisano	R pol
NCP_waterfall_IF0_PL0_F0.ps	action	554939	06 Dec 2006 - 18:50	DjPisano	L pol, Feed 1
NCP_waterfall_IF0_PL0_F1.ps	action	553610	06 Dec 2006 - 18:50	DjPisano	L pol, Feed 2
NCP_waterfall_IF0_PL1_F0.ps	action	552495	06 Dec 2006 - 18:51	DjPisano	R pol, Feed 1
NCP_waterfall_IF0_PL1_F1.ps	action	550601	06 Dec 2006 - 18:51	DjPisano	R pol, Feed 2
NCP_waterfall_IF1_PL0_F0.ps	action	549002	06 Dec 2006 - 18:51	DjPisano	L pol, Feed 1
NCP_waterfall_IF1_PL0_F1.ps	action	542099	06 Dec 2006 - 18:51	DjPisano	L pol, Feed 2
NCP_waterfall_IF1_PL1_F0.ps	action	551610	06 Dec 2006 - 18:52	DjPisano	R pol, Feed 1
NCP_waterfall_IF1_PL1_F1.ps	action	550820	06 Dec 2006 - 18:52	DjPisano	R pol, Feed 2
tsys_qband_p0f0.ps	action	591652	29 Aug 2007 - 21:20	DjPisano	L pol, Feed 1
tsys_qband_p0f1.ps	action	577112	29 Aug 2007 - 21:21	DjPisano	L pol, Feed 2
tsys_qband_p1f0.ps	action	602899	29 Aug 2007 - 21:21	DjPisano	R pol, Feed 1
tsys_qband_p1f1.ps	action	573043	29 Aug 2007 - 21:21	DjPisano	R pol, Feed 2
tcal_qband_p0f0.ps	action	626090	30 Aug 2007 - 01:16	DjPisano	L pol, Feed 1
tcal_qband_p0f1.ps	action	596265	30 Aug 2007 - 01:16	DjPisano	L pol, Feed 2
tcal_qband_p1f0.ps	action	617306	30 Aug 2007 - 01:16	DjPisano	R pol, Feed 1
tcal_qband_p1f1.ps	action	592971	30 Aug 2007 - 01:17	DjPisano	R pol, Feed 2