FORS1 Quality Control and Data Flow Operations

FORS1 Service Mode:
Frequently Asked Questions

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Here you find the answers to some frequently asked questions about FORS1 SM data processing and distribution. If you do not find the answer to your questions here, do not hesitate to contact us.

SM DATA PIPELINE PROCESSING

Which Instrument modes are pipeline supported?

The following modes are currently pipeline supported:

IMAGING (bias and flat-field correction);
LONG SLIT and MOS spectroscopy (bias, flat-field and 2D-wavelength calibration, distortion correction (not for LSS), sky subtraction and extraction of object spectra);

If you want to use the spectroscopic FORS1 pipeline you can download it from here.

Can I use the pipeline reduced data for scientific purposes?

You can certainly use the reduced imaging. The 4 port removal is good to within ~1ADU and the flat-fielding accuracy is of the order of 5%. For long slit spectroscopy one should be more careful, since the flat field normalization is still not yet optimized and some reflections due to the LADC are introducing artifacts on the reduced science frames.

Are there any plans to extend the pipeline support to other instrument modes?

Yes. Currently the Pipeline Development Group is working on supporting pre-reduction (debiassing, flat-fielding) of IMAGE POLARIMETRY (IPOL) SCIENCE data.

I am a Visitor Mode user. Can I use the FORS1 pipeline to reduce my data?

The spectroscopic FORS1 pipeline is available from here.

I have received my Service Mode data. I have noticed that the master calibrations are smaller than the raw frames. Can anybody tell me why and what I should do to use them?

The current version of the FORS1 pipeline trims the pre-scan regions in all processed frames, including master products. For the location of these regions see here for the old CCD (until March 25, 2007) and here for the new CCDs (since March 28, 2007). If you want to use the pipeline master calibrations to reduced unprocessed data, you have to trim the raw data accordingly.

I want to use the zero points I found on the web to calibrate my pipeline reduced imaging. How should I proceed?

First of all you should proceed with great care. These zeropoints are intended for instrument monitoring and not for scientific calibrations (see here). The photometric zero points logged on the web pages are normalized to electrons/second and corrected with default colour and extinction terms (airmass 0), which may deviate from the actual ones (see here). To apply such zero points to the images reduced by the FORS1 pipeline included in your SM package, you have to multiply the measured flux values (ADU) by the average conversion factor.

SM DATA DISTRIBUTION

Where can I find information about the execution status of my Service Mode programme?

This information is provided by the User Support Department and can be retrieved using the following form.

When will I get my Service Mode data?

A service mode package is prepared by QC and the DVDs are burned by the Archive Team once the User Support Department has declared a program completed. For the general policy, have a look here. Usually the programmes are packed within one month from the User Support Department request. This time interval takes into account:
- the time taken by the data to be shipped and received by the Archive in Garching (usually one week)
- the time required by QC to download, process and certify the data quality
- the time required by QC to prepare the data package
- the time required by the Archive to burn and ship the DVDs
Data packages normally reach the PI within 1-2 weeks after being burned.

Do I have to submit a request to receive my Service Mode data package?

No. Service Mode programmes are declared completed by the Users Support Department. This signal is sent to the Data Flow Operations Group which then prepares the SM package. The data are copied onto CDs/DVDs and sent to the PI as soon as possible.

Is it possible to have a partial release of my Service Mode data before the programme is completed?

As a general rule, no. Exceptions are pre-imaging and special programmes. For the general policy have a look here.

SM OBSERVING

Where can I find general information about the Service Mode Observing?

A complete description of Service Mode Observations can be found here. Support during the preparation of SM observations is given by the User's Support Department.