FIRE – Updates

FIRE – Updates

Here we correct some erroneous information in the current manual

Light pattern on FIRE images:

UPDATE: As of April 17th, 2022, the FIRE front window has been cleaned and the issue has been fixed

In March 2022, a light pattern has been reported in the FIRE acquisition images. Further investigation revealed that the pattern is due to residual on the dewar window. This means that images obtained with the Spectral Array are also affected.

Example of light pattern on the Acquisition array
Residual on dewar window

Afternoon calibrations should correct for this and the effect on reduced spectra should not be significant. Long-slit data could be affected more than echelle, since the offsets are larger. The instrument team is working on a solution. 

FIRE noise pattern:

Resuming operations after the uncontrolled warm up of FIRE in the March 2020 due to the compressor failure a light noise pattern has been noticed on the detector. This pattern does not seem to affect data reduction or the overall instrument efficiency, provided all standard calibration files are properly obtained and used.

Time keyword on headers:

Currently the header keyword ACQTIME1 is the one that most accurately reports the starting UT time of a single exposure. 

It has been noted that there is a discrepancy between the keywords UT-TIME and ACQTIME1. When a loop is executed, the ACQTIME1 is updating correctly while the UT-TIME keyword remains the same for all images obtained during the loop. 
To correctly update the UT-TIME keyword, the following formula could be used: 

  • UT-TIME correct  = UT-TIME header + exposure time + readout time  (for single frames)
  • UT-TIME correct on loop N = UT-TIME of + (ACQTIME1_loop(N) – ACQTIME1_loop(1) )    (for loops)

Readout times differ according to the readmode – refer to the manual for more details. 

Acquisition Camera:

The correct pixel scale for the acquisition camera is 0.147″/pixel 

Slit size: 

The correct length of the echelle slit is 6 arcseconds  and for the long slit is 40 arcseconds with the exception of the 12″ slit that is 56″ long. 

Software access: 

The fire software can currently be accessed also from the Llama work station 

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