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Q-band Characterization October 2004

Objectives

• General Checkout (confirm computer controls, confirm optics/beam offsets, etc.)
• Determine the calibration: .
• Quantify the spectral baseline performance.

Observations

1. Perform Hot/Cold load test on the telescope.

The hot loads consist of the vane and the traditional absorber. The cold loads consist of liquid nitrogen and cold sky. Use the DCR to take data with the noise diode (CAL) firing on and off. Use the SiO? transition frequency of 43122.080 MHz and a bandwidth of 80 MHz.

Also need additional frequencies near the upper and lower frequencies of the receiver's band in order to track how efficiency changes with frequency. Three is a minimum, five would be better. More than this probably won't be worth the effort -- RJM

Gary Anderson says the usable frequency range is 41-47 GHz. So maybe the following frequencies:

41000.00, 42820.587 (SiO? v=2, J=1-0), 43122.080 (SiO? v=1, J=1-0), 45000.0, 47000.0

Issues:

• Check linearity. The large difference between hot and cold may put the systemout of the linear regime. The CAL counts should be the same in the hot and cold data.
• CAL strength. The cal must be large enough such that it is not in the noise for the hot load data.

2. Astronomical calibration.

Follow an astronomical calibrator as it rises and sets. Perform PEAK, FOCUS, and TIPPING observations with the DCR and NOD observations with the ACS to determine the calibration as a function of frequency and elevation.

• DCR configuration (Freq = 43122.080 MHz, BW = 80 MHz)
  • Balance IF rack (need not be on source since )
  • PEAK (2 minutes)
  • FOCUS (1 minute)
  • TIPPING (about 10-15 minutes) (every 2-4 hours only!)

• ACS configuration (2 beams x 2 Pol x 2 freq = 8 IFs; 800 MHz BW)
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (40.4, 41.1) GHz
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (41.8, 42.5) GHz
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (43.2, 43.9) GHz
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (44.6, 45.3) GHz
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (46.0, 46.7) GHz
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (47.4, 48.1) GHz
  • Balance IF rack / Balance ACS
  • NOD (1 minute ON, 1 minute OFF) - Freq (48.8, 49.5) GHz

Issues

• Calibrator. From the Ott et al. calibrator list only 3C286 and NGC7027 are good calibrators over 40 GHz. We need the calibrator to be up in the late evening when the thermal gradients are minimized. Planets?

3. Spectral Baselines

• Perform spectral line check by observing different transitions across the band on a weak and a strong continuum source. Perform calibration with the vane (ON/OFF) and a nearby astronomical calibrator (ON/OFF).

• Deep integration. Does the noise integration down as expected?

-- DanaBalser - 27 Oct 2004