Spectrograph Data Format

ASWFC holds Spectrograph data files and images from two stations: Culgoora and Learmonth. The data files are binary daily files. They are available on the ASWFC website and from the ASWFC data server.

The Culgoora and Learmonth file names have the following forms, repectively.

SPECyymmdd
LMyymmdd.srs

where:

• yy = year
• mm = month
• dd = day

Each file contains the following group of three sections, repeated for each scan (ie, every 2 seconds).

• Header
• Channel header
• Channel data

Details these sections follow.

Header

Each Header consists of eight 1-byte fields as follows.

Notes:

• year value: +1900 or 2000
• the Data_OK and unused fields contain no useful data

Channel header

Each Channel header section contains the following fields for each supported channel (frequency band).

Note: The three fields Resbw (Resolution band), Ref-level (reference level) and Range are configuration details for the instrument.

Culgoora supports 4 frequency bands:

• 18-57 Mhz
• 57-180 Mhz
• 180-570 MHz
• 570-1800 MHz

Learmonth supports 2 frequency bands:

• 25-75 Mhz
• 75-180 MHz

Channel data

For each supported channel (frequency band) there are several 1-byte amplitude (dBm) values for frequencies in the band:

• Culgoora has 501 amplitudes per channel
• Learmonth has 401 amplitudes per channel

Note: If the top bit of an amplitude value is set, the value is 256 + the lower 7-bits.

Alternative description

Below is a description of the Culgoora spectrograph data file format that might also be useful.

There is one data record every 3 seconds. A record consists of 2044 bytes arranged as follows:

• record header 8 bytes
• A-band header 8 bytes
• B-band header 8 bytes
• C-band header 8 bytes
• D-band header 8 bytes
• A-band data 501 bytes
• B-band data 501 bytes
• C-band data 501 bytes
• D-band data 501 bytes

where the record header consists of:

• year 1 byte char
• month 1 byte char
• day 1 byte char
• hour 1 byte char
• minute 1 byte char
• second 1 byte char
• data OK 1 byte char
• unused (=0) 1 byte char

and the band headers are structured like this:

• start freq 2 byte int
• end freq 2 byte int
• resolution 2 byte int
• ref level 1 byte char
• range 1 byte char

The data run upwards in frequency and the sampling is linear:

• A-band is 18-57 MHz
• B-band is 57-180 MHz
• C-band is 180-570 MHz
• D-band is 570-1800 MHz

For example:

• the first datum in A-band should be at 18.0 MHz
• the second should be at 18+((57-18)/501) MHz
• the third should be at 18+2x((57-18)/501) MHz
• etc