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

Time	Presenter	Topic
12:00	Science Lunch	Visiting Astronomers Mapping Projects
1:15	Langston	Quick Summary of Review goals
1:30	Garwood	Overview of Pipeline
1:35	Masters	Overview of Pipeline
1:50	Langston	Science Use Cases
2:10	All	Discussion

Discussion topics:

• 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.

Meeting Outcomes

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 calibration observations.

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 is used. Do NOT 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:

• Replace pipelineOrion with pipelineTMC
• Replace imageOrion with imageTMC

Calibration Documents

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 document 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.

-- GlenLangston - 2010-06-15

• Thum2.pdf: Calibration presentation from IRAM summer school

• pdbi-amp-cal.pdf: Amplitude Calibration detail

• kramer_1997_cali_rep.pdf: Cleaner version of IRAM calibration document