For default processing, there will be one table per band and one entry for each mode of coaddition. If processing for each individual scan was requested, there will be entries for each scan as well as the coadded strings.

For each source, the first page of tabular output will summarize some of the input parameters. More information about modified processing is available.

Each table contains the following columns:


This is the scan number as identified on the scan track plot. The scans are numbered in the order they crossed the target. The coadded strings have the following SCAN numbers:

999 is the weighted mean with weights of 1 or 0.5 (for a few noisy detectors)

1001 is the straight mean.

1002 is the statistical median, formed at each point, of all the data scans coadded. If the number of strings is even, the average of the two middle data values is taken at each point. The final median string is Hanning smoothed to reduce high frequency noise.

1003 is the noise-weighted mean string. The weighting factor is 1/SIGMA2, where SIGMA is the root-mean-square residual on each scan after a baseline is fit to the data outside the signal range and subtracted.


The distance in arcminutes between the detector center and target position along the East-West axis.


The distance in arcminutes between the detector center and the target position in the cross-scan direction.


Scan angle measured in degrees East of North.


Satellite Operations Plan (SOP) and Observation (OBS) numbers for individual scans. For coadded data strings SOP = 0 and OBS = total number of data strings coadded.


For individual scans, the detector number (see the IRAS Catalogs and Atlases: Explanatory Supplement[1988, ed. C.A. Beichman, G. Neugebauer, H.J. Habing, P.E. Clegg and T.J. Chester, Washington, DC: GPO]).For coadded data it is the negative of the total number of strings coadded.


The detector size (in arcminutes) cross-scan. It is set to -1 for coadded data.


The rms deviation in mJy of the residuals after the baseline subtraction.


The signal-to-noise ratio (PEAK/SIGMA). This quantity and the next four are given only if a plausible signal could be identified by SCANPI.

Otherwise, the words "Improbable Signal Range" appear. To determine if a real signal exists, the three highest points within the signal range are identified; if the middle one is the maximum of the three and the peak is larger than twice SIGMA, then a plausible source is considered to exist.


The maximum (in Jy) within the signal range specified.

zero xings

Locations of zero-crossings, X(1), X(2), in arcminutes. The zero crossings are defined as he first locations, moving outward from PEAK, where the string crosses the baseline for one or more samples.


An estimate of the total flux density (in Jy) from integration of the coadded string or scan between the zero crossings.


An estimate of the total flux density (in Jy) from integration of the coadded string or scan between fixed points defining an integration range. This range is set using the input parameter SIGLS and defaults to 2, 2, 2.5 and 4 arcminutes at 12, 25, 60 and 100 µm.


The width in arcminutes of the signal at 25% of PEAK.


The width in arcminutes of the signal at 50% of PEAK.


The in-scan deviation of signal peak from the user-specified target position in arcminutes. The location of the peak is taken to be the center of the best-fitting template. The position of signal maximum is used if no template was fit.

Template amp

The flux density (in Jy) from the best-fitting point source template.

Tmp. corr. coeff.

The correlation coefficient characterizing the best fitting template. It should be emphasized that this cannot be compared directly to the correlation coefficients in the IRAS Point Source Catalog. These coefficients run much higher, mostly because of the larger number of points produced by over-sampling. A typical ``good" point source will have a coefficient greater than 0.995 at an SNR above 20.

Optional Detailed SCANPI Printout

Optionally setting NOPRNT=0 causes additional detailed information to be printed, including:


The polynomial fit for the baseline (Cx2+Bx+A), where the coefficients are in mJy and x is in arcminutes.


This is the same as SIGMA in the tabular summary.


Background value at input position (same as A in baseline, above) expressed in MJy/steradian.

total flux

Integrated signal estimates, same as fnu(t) and fnu(z), with the signal range and zero crossings given in arcminutes.


The full width at various fractional levels.

Coadded/Scan Profile Plots

By default, profile plots are made for the four coadded strings only. The plots are labeled by scan number as described under the tabular output. The horizontal axis is distance from the target position in the in-scan direction in arcminutes; the vertical axis is flux in W/m2.

The plot for SCAN 999 shows the interpolated and resampled data with the baseline left in and the baseline fit indicated. The other three coadded strings (SCANs 1001, 1002 and 1003) have the baseline fit subtracted but indicate the signal range and the background range. All four types of plots (and the individual scans, if requested) show the template fit, if a template was successfully fit to the data.

Summary Plots for Individual Scans

Summary plots are generated only if the option to plot individual scans is activated. The following quantities are plotted vs OFFSET (in arcminutes): TEMPLAT AMPL, fnu(Z), and WIDTH (50%). Measurements from each scan are represented by a horizontal bar whose size equals the detector cross-scan size. Measurements on scan 999 are also shown, with a bar size equal to 1'.

Scan Track Plots

Scan tracks (showing the paths of the detector centers) are plotted for all the data. These plots are in the usual astronomical convention, with North up and East to the left. Each scan is labeled by scan number at its beginning.

File Output (optional)

The median scans file "spimed" contains the coadded data strings in an ASCII format. Note that the fluxes are in DC calibrated W/m2. (See the section on IRAS data characteristics for more information on the "AC/DC effect".)

In order to get fluxes in Jy from the raw fluxes, you must divide by the equivalent band pass and apply the DC to AC correction factor. The correction factors used are listed at the bottom of the SCANPI tabular output and are about 1.308, 1.277, 1.060 and 0.98 at 12, 25, 60 and 100 µm. The equivalent band passes are (13.48, 5.16, 2.58 and 1.0)x1012 Hz. In addition, when computing integrated fluxes from the raw fluxes, the integral must be normalized by the integrated point source response which is 0.82, 0.844, 1.437, and 3.234.

The summary table files "spisum" are the same as the printed tables.

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