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DetectorThis page gives a summary of the various readout parameters that you should be aware of when using INGRID.
The "slow" readout mode should always be used for INGRID. This can be invoked with:
SYS> rspeed ingrid slow
(The fast readout mode can sometimes cause a problem with the camera server and is not recommended.)
Note that the detector cannot be binned.
When performing science observations with INGRID, one must select an appropriate readout mode. The default and most straightforward mode, correlated double sampling (CDS), can be selected with the command:
SYS> rmode ingrid mndr 1 1
When taking exposures in this mode: (a) the array is reset, (b) a pre-read is taken, then (c) a post-read is taken at the end of the integration. The pre- and post-reads are stored in extensions  and  respectively of the fits files rxxxxxx.fit.
One can change the command to:
SYS> rmode ingrid mndr <Nr> 1
to invoke an MNDR (multiple non-destructive reads) mode, where <Nr> is the number of reads. This means that <Nr> pre-reads and <Nr> post-reads are performed. The pre-reads are averaged and written to extension  and similarly the average of the post-reads are output to extension . The purpose of this mode is to reduce the readout noise, which decreases with the square root of the number of reads. This mode should only be used for observations with very low backgrounds where the readout noise becomes dominant. Normally we recommend the use of <Nr>=1.
When performing infrared imaging, one is restricted to short exposure times to avoid saturation from the sky background. This leads to the creation of large numbers of fits files and increases the observing overheads due to the time it takes to write to disk. For this reason, there exists the option to average a number of exposures before writing to an output file. After all the exposures are taken, the pre-reads and post-reads are separately averaged; the averaged pre- and post-reads are then written to disk as rxxxxxx.fit and rxxxxxx.fit respectively. This mode can be invoked with the command:
SYS> rmode ingrid mndr <Nr> <N coav>
where <N coav> corresponds to the number of exposures to be averaged.
Here is an example to illustrate the most general case:
SYS> rmode ingrid mndr 3 5
SYS> run ingrid 10
In this instance:
For more details on the readout of INGRID see here.
It is possible to use INGRID like a TV camera, by continuously reading out the detector and displaying the images on the real time display. One possible application for this is when you are preparing to take sky flats and you want to monitor whether the sky is dark enough to proceed. To set this up, type:
SYS> multglance ingrid <N> <exp time> &
This will produce a sequence of <N> exposures of <exp time> seconds. For example:
SYS> multglance ingrid 999 2 &
Once you have finished with the movie mode you can either press control-C or type:
SYS> abort ingrid
To optimise INGRID's performance as a "TV camera" it is recommended to first revert to the standard readout mode:
SYS> rmode ingrid mndr 1 1
A number of storage modes are available for INGRID, and are discussed in more detail here. However, as both the current INGRID RTD (real time display) and the INGRID quick look package only support the "normal" storage mode, it is generally recommend to always use this. With the "normal" mode, the pre-read is put into the first extension of the fits file (i.e. rxxxxxx.fit) and the post-read into the second extension (i.e. rxxxxxx.fit). It can be invoked with:
SYS> storemode ingrid normal
Note that INGRID differs from LIRIS in this respect, as in the latter case the "diff" storage mode is generally preferred.
By default, the whole of the INGRID chip will be read out. It is possible, however, to define up to four readout windows, although this is discouraged because it is not compatible with the INGRID quick look package.
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