Once the telescope's beam had been determined and its aperture efficiency measured, other sources could be observed. Several observational tasks were performed. Nominally, a calculation was performed to ascertain whether or not Jupiter would be observable with our telescope; a measurement was made of the brightness temperature of the moon; and we measured the flux density of the supernova remnant Cassiopeia A.


Is Jupiter Observable?

The flux density of Jupiter is ~10Jy, where 1Jy = 10-26W/m2/Hz at 4 GHz,. It is a measure of the power received from Jupiter per unit area per unit frequency. Jupiter has an angular size of 46" which is much smaller than our telescope's main beam, thereby making it effectively a point source.

From the astronomical Calibration section, the aperture efficiency was found to be 48% and the delta Trms was 11mK. The signal generated by Jupiter at the telescope must at very least equal delta Trms to be considered detectable and would ideally be greater than 3xdelta Trms for a convincing detection.

Accepting Jupiter's flux density to be 10Jy, the resultant antenna temperature would be 13mK based on the relation derived in the discussion of aperture efficiency. Therefore, any detection of Jupiter would be marginal at best.


The Brightness Temperature of the Moon

Luckily, while the declination of the moon was high enough that it could be observered, several observations were made in trying to ensure it passed as close to the centre of the beam as possible. The best of these was done on March 28, 1996, as the moon transited at 20:20 MST. Unfortunately, the observation was prematurely terminated just after the peak was reached. However, a new observing run was begun right away, meaning that the baseline at the time of the transit could be estimated by extrapolating back in time from the later observation.

Recognizing that there are a large number of errors in our estimations, such a crude method of estimating the baseline voltage is far from the predominant source of uncertainty. From the later observation, the baseline at the time of the moon's transit can be estimated to be ~2.050 +/- 0.005V. The peak voltage recorded was 2.215+/-0.005V. This implies an amplitude above the peak of 0.165+/-0.01V. Using the conversion from voltage to temperature (from the calculations of the receiver and system temperatures) yields an antenna temperature of 6.8K. The brightness temperature was then found to be 157K using the relation:

Tb = (Tant x lambda2)/(Aeff x solid angle),

where the solid angle 6.75x10-5sr. This is within the range of 110 - 380K quoted by Zeilik, Gregory and Smith.


Cassiopeia A: An Extra-Solar System Radio Source

The observation of Cassiopeia A was carried out on April 12, 1996 at 10:11am MDT. The measured amplitude voltage above the sky background was 0.04V which corresponds to an antenna temperature of 1.65K.

The brightness temperature of the supernova remnant Cas A was calculated to be 1228K using the relation for Tb above, the effective aperture calculated in the Calibration section, and a solid angle of 2.1x106sr. The flux density was then found to be 1270Jy. From the literature D.A. Green A Catalogue of Galactic Supernova Remnants (1995 July version) Cas A has a flux density of 2720Jy at 1GHz. Using a spectral index of 0.77, the flux density at 4GHz was calculated to be 935Jy. Comparison of the accepted and measured values reveals a discrepency of less than 20%, which is fairly impressive considering the doubts created by the consistent construction difficulties we experienced.


Flying Saucers and Little Green Men

Because drift scans require little personal interaction, it is possible to record data continuously. During the Taurus A scans, an anomalous signal was detected several times. It occured at approximately 4:50 UT on March 29 and drifted at a non-sidereal rate. This would imply that the source of the signal is within the solar system or moving very fast. However, we were unable to connect the signal with any known radio emitter such as a planet. If it was a Earth orbiting satellite, it could not be in a geostationary orbit due to its non-zero declination, as well as it not appearing at the same time each day. It could be a non-geostationary satellite that coincidentally has an orbit that carried it through the main beam at nearly the same time every day. With its position being in the ecliptic, it could also be an interplanetary probe. NASA was contacted but stated they had no known spacecraft at a position corresponding to the anomalous source. Also, the signal profile was considerably narrower than our beam width which implies a quickly moving source. Agent Mulder has been consulted but has yet to respond.


Originally, we had planned to include a measurement of the angular width of the Galactic plane. However, it was impossible to do so without some means of measuring the variation in the gain of the signal, which varied by up to 10% over measurements of a few hours. A possible solution to this limitation would be to install a noise diode which would emit a signal of known strength at regular intervals. Variations in the response to this pulse would provide a means of quantifying the change in gain over time.

This report has discussed the construction and operating procedures of a single dish radio telescope. We have attempted to emphasize the key concepts needed to calibrate and operate this device as well as what we consider to be current limitations to its operation which remain to be addressed. We had barrels of fun!