KFPA Pipeline Calibration and Imaging Review
NRAO will hold an internal review of the KFPA imaging pipeline on Thursday June 17, starting
with the science lunch discussion of science priorities for GBT imaging projects. We will continue at 1:15 with the
agenda centered on scientific requirements for the pipeline. We intend to be finished in time for the
technology development talk.
The top goals of the pipeline review are to update the scientific staff on the status of the pipeline and to
get feed back on some design decisions and default pipeline parameters.
Agenda and Topics
|| Science Lunch
|| Visiting Astronomers Mapping Projects
|| Quick Summary of Review goals
|| Overview of Pipeline
|| Overview of Pipeline
|| Science Use Cases
- Data products
- Set of calibrated spectra for a single mapping session
- Image cube from default spectral region
- Calibration Options & Default Calibration Units
- T_mb, with vector T_cal values
- atmospheric corrections
- Mapping Options
- Pixel/Image sizes
- Region etc
- Convolution function
- Data products will not include
- Baseline fitting (Observer will use IMLIN, etc)
- Selection of individual lines (Observer will use ISPEC, etc to find the lines)
- Combine different observing sessions (done by observer after all sessions are completed)
We also realize that follow on tools are needed for efficient processing of the pipeline products.
- Tools for identifying continuum, fitting baselines and selecting frequency ranges of lines
- Intra-beam calibration; steps to get gain and intensity agreements between different array beams and polarizations
- Re-sampling the frequency grid to allow merging of observations at different dates (to deal with the topocentric clock in the spectrometer sampler
- Default output products, ie continuum image over 50% of band and data cube with 2 channels averaged to reduce sluggishness of display tools.
The results of this review are to determine appropriate default calibration parameters.
There is a tension between all the calibration/mapping options and a complete automatic pipeline default.
We would like some consensus on these parameters for the two generic use cases
- Position Switched calibration
- Frequency Switched calibration
We also want feedback on work to date, and guidance on priorities for the next version of the pipeline.
Example Pipeline Experience
We'd like all attendees to get some experience before the meeting,
by either selecting a test dataset for imaging or using a data
set of their own. All gbt spectrometer date can be imaged with the
pipeline, but with different levels of success, depending on the
Below is a list of Linux commands that will calibrate GBT KPFA test observations of Orion A.
These commands can be copied and pasted into a linux terminal.
The linux terminal must be one of the computers that can run AIPS. These computers include
planck, newton, euler
| mkdir /home/scratch/$USER/pipeline
|| ; echo "... Make a working directory"
| cd /home/scratch/$USER/pipeline
|| ; echo "... Go to pipeline directory"
| cp /home/sandboxes/kfpa_pipeline/demo/pipelineOrion .
|| ; echo "... Copy pipeline configuration file to scratch"
| source pipelineOrion
|| ; echo "... Run pipeline "
| cp /home/sandboxes/kfpa_pipeline/demo/imageOrion .
|| ; echo "... Copy image configuration file to scratch"
| /home/sandboxes/kfpa_pipeline/doImage imageOrion 11111 *20_20_23703_0.sdf
|| ; echo "... Image Cube produced from calibrated spectra (.sdf files)"
| casaviewer *cube.fits
|| ; echo "... Examine the Image Cube"
These linux commands
are also in the pipeline demo directory. The demo consists of
two major components:
- Calibration of spectra is done using GBTIDL and configured by pipelineOrion
- Imaging the calibrated data, using script imageOrion
The process of making images is done using scripts to control AIPS task inputs.
The imaging step requires an EMPTY
AIPS catalog. In the example above, AIPS ID 11111
use your own AIPS number, as ALL DATA WILL BE DELETED
The AIPS data will remain in the catalog for that AIPS ID, until the next pipeline execution.
Or you can use TMC data:
Finally notation is an issue. Many use "Tools of Radio
Astronomy", by Rohlfs and Wilson, but there is some inconsistency
in the description. The IRAM Calibration
seems to have a good mix of equations with examples
and deals with similar issues to the GBT. How about this
as the reference? or suggest an alternative.
- Thum2.pdf: Calibration presentation from IRAM summer school