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Ballima (Tidbinbilla 70-m) Radio Telescope Guide to Observations |
Introduction
A limited amount of time is available on the 70-m antenna at the Canberra Deep Space Communication Complex (Tidbinbilla), named Ballima, for spectroscopy in a service observing mode and other single-dish observations. Proposals should be submitted to ATNF in the normal way for review by the Time Assignment Committee (TAC). Proposals are prioritised according to the TAC rankings with the highest priority sources observed first. Spectroscopy observations will be conducted in service mode so the proposers are not required to be present at Tidbinbilla although they may do so if desired. PIs are notified by e-mail when their observations have been made and data are made available either by FTP or on CD-ROM. Accepted proposals remain active for 12 months. Proposals to use the 70-m antenna for purposes other than spectroscopy may also be submitted however please contact us before applying to assess the suitability of your proposal.
Time Allocation
As part of the Host Country agreement with NASA, a fraction of time on Ballima is allocated for independent scientific activities sponsored by the Australian Government. In the past this time has been used mainly for VLBI observations but not all of it has been utilised, either because it did not coincide with the availability of other LBA antennas or because the period of the allocation was too short to provide useful (u,v) coverage. It is this time together with surplus time allocated to NASA spectroscopy projects that is being made available. Proposers should bear in mind that the amount of available time is likely to be at the level of 200 hours per year. If large amounts of time are required for a project, please consider applying for time directly through the DSN (see http://dsnra.jpl.nasa.gov/). Typical allocations are 5 to 12 hrs in length with limited LST ranges. Therefore projects that can be divided into observation periods of 1hr or less are more likely to be observed than those requiring long integrations on a single day.
Likely availability of Ballima
A high priority for the DSN is tracking spacecraft at Mars. Therefore it is unlikely that much time will be available for radioastronomy while Mars is above the horizon.
Receivers
The following table lists the available receiving systems on the 70-m antenna.
Receiver |
Band (cm) |
Frequency Range (GHz) |
Illuminated Diameter (m) |
Beam FWHM (arcmin) |
Tsys (K) |
Peak Sensitivity (Jy/K) |
Polarisation |
Instantaneous receiver bandwidth (MHz) |
Status |
L-band |
18 |
1.610 - 1.705 |
70 |
8 |
25 |
0.9 |
LCP |
95 |
available |
S-band maser |
13 |
2.270 - 2.300 |
70 |
6.4 |
16 |
~1 |
LCP or RCP (b) |
30 |
available |
S-band hempt |
13 |
2.200 - 2.300 |
70 |
6.4 |
25 |
~1 |
LCP or RCP (b) |
100 |
available |
X-band |
3 |
8.183 - 8.633 |
70 |
1.8 |
25 |
~1 |
LCP and/or RCP |
100 |
available |
K-band |
1 |
18.0 - 26.5 |
70 |
0.8 |
40 |
1.5 |
LCP and/or RCP |
400 (restricted frequencies) |
available |
(a) With typical atmospheric contribution
(b) Dual circular polarisation S-band observations are possible with one polarisation through the hempt and the other through the maser.
Signal Path
Following down-conversion the signal from any receiver can be split, if needed, and the centre frequency of those two IFs can be tuned independently. For example, if high spectral resolution observations of both the 1665 and 1667 MHz OH transitions is required, the signal from the L-band receiver can be split and the two IFs mixed so that IF1 is centred on the 1665 MHz transition and IF2 is centred on the 1667 MHz transition. The correlator could be configured to take 1 MHz bandwidth in each IF with 4096 chans each.
The 1-cm (18.0 - 26.5 GHz) System
Sensitivity.
For a reference pointing observation, single polarisation:
RMS = 2.6E-3 * G(El) * Tsys / sqrt(W*t/N) Jy where Tsys is in K (typically 40 to 50K), W is total bandwidth in MHz N is number of spectral channels t is time on source in sec, and G(El) is the antenna gain as a function of elevation G(El) is described by the polynomial: G(El) = R0 + R1*El + R2*(El^2) where R0 = 3.58788e-1 R1 = 2.87243e-2 R2 = -3.219093e-4
The peak in the gain curve occurs at 44.6 degrees elevation and is above 0.9 between elevations of 27 and 63 degrees.
Note the above equation does not include a correction for opacity which in winter is typically 0.05.
There is now a Sensitivity Calculator to help in planning observations.