NATIONAL RADIO ASTRONOMY OBSERVATORY

Green Bank, West Virginia

DATE:

TO: VLBI Network

FROM: R.J. Maddalena

SUBJECT: NRAO-GB 140-ft telescope calibration, 1.67 GHz, September 1992

Calibration of Antenna Efficiency

The temperatures used throughout the calibration of antenna efficiency, eta A, were determined from 70 pointing and source temperature measurements obtained during the VLBI session. I have used the assumed flux densities given in Table 1 and the measured antenna temperatures to estimate etaA (when the physical aperture of the telescope is used etaA equals 1.93 TA/S where S is the 1.67 GHz flux in Jy.). At 18 cm, efficiency does not change with position in the sky for the 140-ft.

The average of the derived etaA, 0.5800.003, is extremely close

to what has been derived in the past.

Table 1


Source Flux Density (Jy)
0023-26 7.76 0.62 (2)

0237-23 6.32 1.31 (2)

1245-197 5.08 1.76 (2)

2021+61 2.23 0.18 (1)

2203-18 6.05 0.26 (1)

3C123 42.4 2.6 (3)

3C161 16.8 1.2 (3)

3C218 36.8 4.4 (3)

3C231.0 7.57 1.28 (2)

3C273 45.5 1.9 (1)

3C274 184. 20. (3)

3C286 13.6 0.9 (3)

3C295 19.2 1.5 (3)

3C330 5.81 0.92 (2)

3C348 37.5 5.5 (3)

3C433 10.7 0.8 (2)

3C438 5.66 0.45 (2)

3C454.3 12.9 0.56 (1)

3C48 13.9 1.0 (3)

NGC 7027 1.60 0.10 (1)


References:

(1) Previous reports on the calibration of the 140-ft telescope.

(2) Kuhr et al. (1981, Astr. Ap. Suppl., 45, 367).

(3) Baars et al. (1977, Astr. Ap., 61, 99).