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OPUS OPR 41658
"Transmitting CTE information"

Charge Transfer Efficiency (CTE) will be monitored for the ACS as described in the ACS TIR 1999-03. The OPUS PR 41470 describes the irregular image sizes needed. PR 41481 filed against PROPINST describes two new optional parameters, CTE and AMP. Corresponding to CTE, a new keyword CTEIMAGE needs to be created and populated in the QEKEYWORD relation for the corresponding exposure. The value of CTEIMAGE is derived from CTE values as follows. IF CTE has any of the values JCTWFS, JCTHFS or JCTHFP then CTEIMAGE = FPR. If CTE is JCTWE or JCTHE then CTEIMAGE = EPER. If CTE is absent or set equal to NONE, then CTEIMAGE should aso equal NONE. If CTE is present and not equal to NONE a value of AMP will be given and its value must propagate to a keyword CCDAMP.

This OPR is a late addition to other CTE work (OPRs 41482, 41483 and 41484). Work will be done in the same parallel world as those OPR's.

Date: 26 Jan 2001
From: Jim Rose
To: Alan Welty"
Subject: Re: ACS CTE header problem

I ran the data far enough to parse the internal headers. I found that for most of the data the NUMROWS (JQCCDXSZ) and NUMCOLS (JQCCDYSZ) were zero.


I think that the question is wrong.

The internal header is part of the ICD between the Instrument and the Institute: we do expect all the mnemonics in the internal header to be populated. You are asking me what portions of the internal header are "really" important. It's kind of like asking what portions of the PDB (of which the internal header is a part) are "really" important.

Respecifying what "should" be populated in the header is effectively changing the meaning of the interface, and I do not feel that I am in the position to begin renegotiating the ICD.

In sum, I feel that all mnemonics in the internal header should be populated correctly.

Alan D. Welty" wrote:


Tom forwarded your message to me. There are a couple ways we can fix this, but lack of manpower could keep it from happening soon.

If I understand correctly, there isn't to be any special processing done on the CTE images, so the X & Y dimensions may be all you need. If processing were to be done, things like overscan keywords would also need to be populated correctly. I guess what I'd like from you is your assessment of what missing info you would need to proceed with the CTE data. (I'd like to avoid asking for changes to get X & Y into the headers, only to find out later that other items are also needed.)

OPUS OPR 43216
"CTE Image Size"

The CTE images do not supply the image sizes in the internal header. This presents a difficulty for Generic Conversion. At a future date the flight software may supply this information, but the following workaround should be used for now. The value of internal header keyword CPRWORDS may be interpreted as follows to give the values for NAXIS1 and NAXIS2 in the science headers.


The first two rows will apply to WFC EPER and FPR images, and values of NAXIS1 and NAXIS2 apply to each of the two imsets. Rows 3 and 4 refer to the single-chip HRC images. (The value of CTEIMAGE should be obtained from CTE as described in PR 41658).

In addition to TRANS OPR 14658 mentioned above, OPUS OPR 41470 deals with the image sizes of ACS CTE images.