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The following section describes the BS2 data file format, adapted from the NSF system. Each data file has a unique filename, the first character of which specifies the data type:
All data are in ASCII format, using only character codes 10, 13, and 32 to 126 decimal inclusive. ASCII codes 9 (tab), 12 (form feed), 27 (escape), or 127 (delete) and codes greater than 127 are not used. Data values are either space separated or comma separated.
Files consist of a header section containing ancillary scan and Quality Control information, followed by the data:
| Type | Description | Name format |
|---|---|---|
| Reference data: | ||
| L | Lamp spectral output (Wm-2 nm-1). The lamp irradiance at the diffuser mounted in the calibration configuration, as given in the calibration certificate. | Llabel.dat |
| R | Reference data. Examples include noon solar zenith angles as a function of day number; cosine response functions (where the independent variable is angle) and slit functions. | Rlabel.dat |
| X | Action spectrum or spectral response function. | Xlabel.dat |
| Calibration data: | ||
| P | Measurement of one or more spectral lines (nA). (e.g. Fraunhofer lines, Hg lamp emission). | PyySnnn.xxx |
| W | Wavelength calibration file. | WyySnnn.wlc |
| A | Absolute scan (nA) of system response to calibration lamp. | AyySnnn.xxx |
| C | Irradiance calibration file (Wm-2 nm-1). The ratio of L/A. | CyySnnn.cal |
| F | Calibrated spectral measurement (Wm-2 nm-1). QC check of lamp. | FyySnnn.ddd |
| Calibrated measured data: | ||
| E | Calibrated spectral measurement (Wm-2 nm-1) for experiments. | EyyShhmm.ddd |
| G | Calibrated global spectral irradiance (Wm-2 nm-1). | GyyShhmm.ddd |
| T | Transmission spectra (ratio - no y units). | TyyShhmm.ddd |
| where | yy | = short year (e.g. 99) |
| hh | = hour (UTC) | |
| mm | = minute | |
| ddd | = day number (1-366) | |
| S | = slit width (resolution) code: F = 0.05 (fine), H = 0.37 (high), M = 0.74 (med.), L = 1.48 (low), X = not known. | |
| nnn | = calibration serial number | |
| xxx | = scan index number for individual calibration scans. |
Most users will be interested either in measurements of global irradiance (data type G). Calibrated spectral measurements (data type E) may include measured output from other light sources.
Transmission spectra (data type T) are the ratio of radiation transmitted by the material on test to the output of the lamp and the data ranges from 0 to 1. Multiplying an incident irradiance spectrum (e.g. global irradiance data) by a transmission spectrum for a material will give the theoretical irradiance under say, a cloche (assuming a 90° angle of incidence).
Similarly, action spectra or spectral response functions (data type X) may be used to weight spectral measurements.
Files consist of a header section containing ancillary scan and Quality Control information, followed by the data:
| Line | Parameter | Format | |
|---|---|---|---|
| all types: | |||
| 1 | BS2, | file format identifier | |
| 2 | filename, | char[15] | normally nm |
| 3 | x units, | char[20] | upper case |
| y units, | char[20] | normally W/m2/nm for spectral irradiance files | |
| all measurement types: | |||
| 4 | station name, | char[15] | e.g. 'Rothera01' |
| date, | dd-mm-yyyy | British ISO, long year | |
| day number, | integer | 1 = Jan 1st | |
| time start, | hh:mm:ss | UTC (GMT/Zulu) | |
| time stop, | hh:mm:ss | UTC (GMT/Zulu) | |
| 5 | slit width, | real | units = mm |
| samples per reading, | integer | 0 = variable (adaptive integration) | |
| 6 | last PMT interrupt, | dd-mm-yyyy | British ISO, long year |
| wavelength calibration filename, | char[15] | (upper case) 'none' = wavelength correction not applied | |
| irradiance calibration filename, | char[15] | (upper case) 'none' = irradiance correction not applied | |
| 7 | PMT dark current, | real | units = nA |
| PMT voltage, | real | units = V | |
| electronics (ADC) offset, | real | units = V | |
| 8 | monochromator temperature, | real | units = °C |
| envirobox temperature, | real | units = °C, null = assume no envirobox control | |
| air temperature, | real | units = °C, = room temperature for types P,W,A,C,T & F | |
| global irradiance spectra (type G) only: | |||
| 9 | schedule time, | hh:mm:ss | UTC (GMT/Zulu) |
| solar zenith anlgle, | real | units = degrees | |
| azimuth, | real | units = degrees | |
| direct sun, | char | N=no direct sun, Y=direct sun, null = not known | |
| lamp measurement types (A,C,P,W,F,E): | |||
| 9 | lamp ID, | char[50] | lamp name/code |
| transmission spectra (type T) only: | |||
| 9 | material, | char[50] | material identifier |
| thickness, | real | units = mm | |
| lamp file, | char[50] | (upper case) | |
| all types: | |||
| - | comment | char[255] | (enclosed in double quotes) |
| :data start | |||
| x1 y1 (e.g. wavelength vs. irradiance) | |||
| x2 y2 etc … | |||
| xn yn | |||
| :data end | |||
Note: All unknown or inapplicable fields will be null (blank fields). Numbers in square brackets give the maximum length of character data.
Calibration records are stored in an ASCII data file using the Windows initialisation (INI) file format (section names in square brackets, key=space separated data):
| where | key | = integer calibration serial number |
| filename | = calibration filename | |
| date | = date of calibration | |
| lamp | = lamp identification/serial number | |
| certificate | = file containing lamp calibration certificate data |
The lamp burn record for each lamp is stored as a separate Excel spreadsheet.
