Technical
Mode:Pulsar
Back end:GBPP
Back end Mode:
Procedures:Track
Receiver:X
Switching Scheme:
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Proposal Information
PI:Cordes
Bands: X
Back ends: B
Support Person: F. Ghigo
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Checkout Notes
Waiting on BCPM2
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On Hold Notes
Waiting on BCPM2 or spigot
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Technical
Mode:Pulsar
Back end:ACR12_5
Back end Mode:Spigot card or GBPP?
Procedures:Track
Receiver:L
Switching Scheme:
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Proposal Information
PI:Stairs
Bands: L
Back ends: B
Support Person: F. Ghigo
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Checkout Notes
Waiting on spectrometer spigot
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On Hold Notes
Second part of observations require spectrometer spigot
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Technical
Mode:Line
Back end:SP
Back end Mode:2x1024 10-20 MHz(?)
Procedures:OffOn
Receiver:AL
Switching Scheme:TotalPwr
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Proposal Information
PI:Darling
Bands: AL
Back ends: S
Support Person: F. Ghigo
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Checkout Notes
L-band project already under way; requires PF2 for completion. RFI problem with 11sec radar at L-band; other RFI problems expected with PF2.
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Scheduling Notes
Second half awaits completion of PF2
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On Hold Notes
Second half awaits completion of PF2
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Technical
Mode:Line
Back end:P
Back end Mode:ACF 1x2, 800 MHz, multi-bank; SP: probably 2x1024, 10 MHz, cross polarization
Procedures:OffOn
Receiver:LS
Switching Scheme:TotalPwr
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Proposal Information
PI:Heiles
Bands: LS
Back ends: SP
Support Person: T. Minter
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Checkout Notes
The cross-polarizatio modes of the ACR required but testing can proceed with the cross correlation mode of the SP. Proposal isn't very explicit about the needed SP or ACR modes.
RFI will be a problem.
01/03/03 T. Minter
GBT-02A-053 commissioning report
--------------------------------
Anish Roshi had originally been helping with the commissioning of this
project. January 2, 2003 was my first day in helping commission this
project. Tom Troland and Tim Robishaw were also here to with the
commissioning. Unfortunately, I was not able to learn everything that
Anish had learned before he left. Also, the PI of this project left us
with the impression that only very minimal support would be needed.
This did not turn out to be the case and led to an eventful day.
First, the visiting observers desired to change the way the
commissioning was done from what Anish had been doing - or at least
from what he had shown me. They desired a new procedure and do to
multiple IF observing which had not been successful before this
attempt to my knowledge. Observing was to begin at 7:00 AM but
because of these surprise changes we were not able to get things going
very well until about 5:00 PM. This was mainly due to figuring out
how to setup and balance the IF system and in time spent writing the
new "observer added" procedure that they required.
A few problems where noticed along the way.
IF Balancing
------------
4 frequency bands were desired spread across the entire receiver bands
for L, C and X bands. Only L and C were attempted. In each case all
of the RF bandpass of the receiver was allowed to go through the IF
Rack and Converter Rack. These were able to balance without any
problems. However, at the spectral processor each IF input was only
5 MHz wide. This meant that there was very little power (for example
about 5/700th the power in the Converter Rack output going into the
spectral processor IF input) in the spectral processor inputs. This
made it very difficult to get the spectral processor happy with signal
levels and I still am uncertain that we were in a linear response
regime.
We need to consider having amplifiers after the converter rack and
before the backend or separate narrow band, adjustable filters for
each IF after mixing with LO3 and before the converter rack
attenuators.
Spectral Processor
------------------
There are limitations to what the spectral processor can do that are
not reflected by the M&C system. For example, when the spectral
processor has 8 IF inputs you can only do 10 MHz bandwidth max in
square mode and 5 MHz bandwidth in square-cross mode. The M&C system
allowed you to pick 8 IFs, square-cross mode with 20 MHz bandwidth.
Furthermore, it ran a scan without any errors. I only discovered this
limitation when the data looked very bad - who knows what the spectral
processor acutally did - and when we needed to put filters in front of
several of the IFs before going into the spectral processor to get
ride of interference (which lead to the filter discussion in which
Rick Fisher mentioned this limitation).
Short Scans problems with Antenna and Spectral Processor
--------------------------------------------------------
Troland and Robishaw were also trying to several short scans
(4 seconds long) after doing a cross cut on a source. The short scans
were to be at the start and end of the cross cuts. Sometimes this
would cause the antenna to have trajectory failures. Joe Brandt
indicates that this is due to the requested antenna motion being very
small which the trajectory algorithm does not handle very well.
Secondly, every now and then the spectral processor would have the
problem of not emptying a buffer correctly just before a 4 second
scan. This would cause the 4 second scan to fail since the spectral
processor would not write any data. Mark Clark was called and has
seen this error happen.
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On Hold Notes
Waiting for Spectometer Polarization capability
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Technical
Mode:Pulsar
Back end:BCPM
Back end Mode:
Procedures:Track
Receiver:L
Switching Scheme:
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Proposal Information
PI:Stairs
Bands: L
Back ends: B
Support Person: F. Ghigo
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Checkout Notes
Waiting on BCPM polarization (D. Backer)
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On Hold Notes
Waiting on polarization (spigot or BCPM)
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Technical
Mode:Line
Back end:ACR50
Back end Mode:4x2, 9-level, probably single bank
Procedures:DualBeamSwitch
Receiver:K
Switching Scheme:BeamSw
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Proposal Information
PI:Hunter
Bands: K
Back ends: S
Support Person: G. Langston
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Checkout Notes
Requests 4 transitions, dual polarizations (8 Conveter, racks, ACF inputs, 9-level, 8192 channels) but smoothing by factor of six indicates they may not need multibank mode. Or, they can take more than their requested observing by using other ACF modes. SP would be 4x as inefficient as ACF.
Long integrations will require good baseline shapes.
Beam switching probably better than proposed mode
02/14/03 R. Maddalena
2B-004: I worked with Harvey on checking this proposal out and we found
it to have a few technical flaws. First, the PI's are observing a point
source and desire to observe with both the upper and lower-K-band
receivers simultaneously. Since this is not possible, we'd have to double
their time of the telescope to accommodate them. They also want to
observe 8 transitions simultaneously in two polarizations in a 50 MHz
bandwidth. Although the Spectrometer has 16 inputs and could accommodate
the observations, the wiring between the Analog Filter Rack and the
Spectrometer for the K-band system will only allow up the simultaneous use
of only 8 Spectrometer samplers. We'd have to again double their
telescope time to accommodate the observing.
03/02/03 G. Langston
The multi-molecular line experiment 2B04 can not be done as specified in
the proposal. The PI requests a line at 20.6 GHz and the rest of the
lines are at frequency > 22.5 GHz, so one line can not be observed
simultaneously with the other lines. Can not set up the IF rack
for all other lines simultaneously, because the power levels
are too low in the spectrometer for some lines. This is due to
the observer requiring widely separated frequencies, and the
fiber optic modems driver requirement of not exceeding input power
over the the entire 3 GHz band. This problem might be corrected
by increasing the converter rack gains for modules 1 and 5.
03/12/03 G. Langston
The project 02B04 experiment can not be performed with the current
hardware configuration of the optical modems and convert module gains. Roger
reports that modifications are planned that will allow these observations,
but not until next fall.
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On Hold Notes
Waiting for modifications to hardware for converter gains and config of optical modems Fall 03
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Technical
Mode:Line
Back end:SP
Back end Mode:ACF: 2x2, any-level, single bank, 50 MHz; SP: 2x1024, 40 MHz
Procedures:OffOn
Receiver:LX
Switching Scheme:TotalPwr
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Proposal Information
PI:Yusef-Zadeh
Bands: LX
Back ends: S
Support Person: R. Maddalena
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Checkout Notes
Requires good baselines for wide lines and long integrations. Either SP or ACF would work.
09/12/02 R. Maddalena
Test observations indicate bad baselines in the presence of a strong source.
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Spectrometer (Autocorrelator) Notes
Required: 1N4-0A-50-9 and 1N4-1A-50-9. Or 4N4-6A-50-3 and 4N4-6B-50-3 with a minor loss in efficiency.
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On Hold Notes
Bad baselines
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Technical
Mode:Pulsar
Back end:S
Back end Mode:
Procedures:
Receiver:4L
Switching Scheme:Frequency
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Proposal Information
PI:Cordes
Bands: 4L
Back ends: S
Support Person:
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On Hold Notes
Requires Spigot card
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Technical
Mode:Pulsar
Back end:B
Back end Mode:
Procedures:Track
Receiver:L
Switching Scheme:
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Proposal Information
PI:Roberts
Bands: L
Back ends: B
Support Person: A. Minter
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On Hold Notes
spigot card
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