PTI V2 Data Products
Spectrometer (.spec) File
Spectrometer files are ASCII text files that contain the narrow-bandL-1 V2 data for PTI. The following gives an example of aline from a PTI spectral file:SPEC: 12/11/98 HDC3651 2.332531 3.5096642 5 2.510 2.388 -0.193 -0.435 1.591 3.845 2.312 0.216 0.193 1.113 3.411 2.203 0.514 1.194 1.327 3.880 2.099 0.122 0.812 1.129 2.207 2.011 0.302 1.947 1.007
The line consists of a number of space-delimited fields. Themeanings of these fields are summarized in the table below. Each linecorresponds to a block average of typically 25 seconds of fringedata, not necessarily contiguous. All entries, including time anddelay line position, are mean values for the block.
| field# | content | comments |
|---|---|---|
| | SPEC: | a literal string; each line starts with SPEC to support the grep extraction mechanism from the intermediate .data file produced by vis. |
| | date | UTC date of the observation (mm/dd/yyyy) |
| | target | Target designation (ASCII string) |
| | time | Mean observation time (decimal UTC hours) |
| | DL position | Mean delay line position (m) |
| | Spectrometer pixels | Number of spectrometer pixels (integer) |
Then, for each pixel ("channel") i (1..n), the following fields aregiven:
| field# | content | comments |
|---|---|---|
| 7 + 5*(i - 1) | photon count | Channel N (DN units) (approximately 5 photons/DN) |
| 8 + 5*(i - 1) | lambda | wavelength (microns) |
| 9 + 5*(i - 1) | Coherent V2 | Channel coherent visbility (dimensionless) |
| 10 + 5*(i-1) | Incoherent V2 | Channel incoherent visbility (dimensionless) |
| 11 + 5*(i-1) | ratio correction | Channel V2 ratio correction (dimensionless) |
| 7 + 5*nchan | Frame rate | Fringe measurement frame rate (Hz) |
| 8 + 5*nchan | Baseline | PTI baseline tag |