When Mars is available, it is a good target for several important
Flux, angular size, and elevation information is given below for two dates,
along with integration times for a 1% detection (signal-to-noise = 100) of
Mars, denoted as t100.
- Instrumental polarization: Since Mars is an unpolarized
source, observing it with SPARO will give the combined
Viper/SPARO contribution to the polarization signal.
This is the most important of the "Mars tests".
- Beam shape: Mars, having an angular size of about 10 arcseconds, is
a point source to SPARO and thus can be used to do a more precise
mapping of the Viper/SPARO beam shape. Here, 1 degree scans each
way in elevation and azimuth should give enough information to
check the beam shape. See also the document on "moon scans".
- Off-axis polarization: we want to measure the instrumental
polarization by pointing SPARO at four half power points of Mars'
A zenith opacity of 1.5 or 1 has been assumed in the above estimates, as well
as a surface temperature of 200K for Mars. It appears that the elevation of
Mars is the limiting factor in the integration time required for a 1%
Also note that if we know the integration time required for a signal-to-noise
ratio of N, then the time required for a S/N of M is
tN/tM = (N/M)2
Calibration targets for Austral Summer/Winter 2000 and Austral Summer 2001.