Spitzer Documentation & Tools
IRS Instrument Handbook

6.3  Spectroscopic Data Products

6.3.1             Raw Data

The IRS Raw Data consist of one or more Data Collection Events (DCEs) that have been converted to FITS format files. Each individual DCE corresponds to a separate file. These files are presented as three-dimensional data cubes, consisting of a number of non-destructive reads (samples) at fixed time intervals of the 128128 pixel2 detector plane, where the number of reads N is determined by integration time and corresponds to the number of layers of the FITS data cube. Thus, the imaged spectra have dimensions of 128128N in the DCE FITS file. Each data plane represents one readout of the array. All IRS spectra will contain either 4, 8, or 16 reads of the array between resets. Any ramp duration (exposure time) longer than 14 seconds results in a sixteen plane raw FITS data product.

Table 6.2 lists the number of reads per ramptime availble for each module, and Table 6.3 lists all the raw files which may be delivered for an AOR that includes spectroscopic observations.

 

 

 

 

 

 

 

 

 

 

Table 6.2 Number of reads (samples) per ramptime available for each module.

Ramptime

Number of Reads (Samples)

SH

6

4

30

16

120

16

480

16

LH

6

4

14

8

60

16

240

16

SL

6

4

14

8

60

16

240

16

LL

6

4

14

8

30

16

120

16

 

Table 6.3 Raw Files Delivered.

Name

Description

Format (a)

Channels (b)

Size (kb)

raw.fits

Raw data cube in units of DN.

128 128 N

16-bit int

0,1,2,3

<600

rawb.fits

Raw data cube in units of DN for blue peak-up array. For a spectroscopic AOR, these correspond to Peak-Up Acquisition images.

128 128 N

16-bit int

0

200

rawr.fits

Raw data cube in units of DN for red peak-up array. For a spectroscopic AOR, these correspond to Peak-Up Acquisition images.

128 128 N

16-bit int

0

200

(a) N = number of samples per ramp

(b) 0=Short-Low (SL), 1=Short-High (SH), 2 = Long-Low (LL), 3 = Long-High (LH)