For this page:
THE NERC MST RADAR FACILITY AT ABERYSTWYTH
FILE FORMAT FOR VERSION-0 MST RADAR IQ DATA
All raw MST radar data files are Version-0
However, users are encouraged to make use of Version-2 MST radar data products.
Click here to find out more about the different versions of the signal processing.
These files contain (pre-spectral) in-phase (I) and quadrature (Q) radar return samples.
File naming convention:
File location: /badc/mst/data/mst-raw/iq
Click here for the location of other files.
Archiving convention: YYYY
Click here for a further explanation.
IQ data are not typically recorded and so files exist only when they the data have been stored as part of a special campaign.
The data are stored in non-standard format binary files, as described below:
IQ DATA FILES -------------- File name :- IQyymmdd_hhmm.min RANDOM ACCESS FILE - UNFORMATTED RECORD = 64 BYTES File layout. ------------ Dwell 1,Cycle 1 Dwell 2,Cycle 1 PB+IQD,IQD,IQD,.....IQD,PB+IQD,IQD,IQD,IQD,.....etc... Dwell x,Cycle y ....,IQD,IQD,PB+IQD,IQD,IQD,IQD,.....IQD,IQD,BREC PARAMETER BLOCK ( PB ) ( Start of Each Dwell ) ---------------------- Uses 48 bytes out of 64 available. Following bytes are data values. NB !! PB allways at the start of a record. B = BYTE , I2 = INTEGER*2, I4 = INTEGER*4 LTX B Length of Transmitter pulse ( uSec ). NCC B Pulse Code Resolution. 0 = Uncoded , 1 = 8 uS , 2 = 4 uS 3 = 2 uS , 4 = 1 uS IPI I2 Pulse Repetion Interval ( uSec ). NPP I2 Number of Coherent Pulse Additions. LFT I2 Length of FFT. NAV I2 Number of FFTs Averaged together. NH1 I2 Start of First Height Range ( Bin No. ). NH2 I2 End of First Height Range ( Bin No. ). NBM I2 Beam Number. IY I2 YEAR in Form 90,91,92 etc. IMN I2 MONTH ( 0 - 12 ) ID I2 DAY ( 0 - 31 ) IH I2 HOUR ( 0 - 23 ) ] IM I2 MINUTE ( 0 - 59 ) ] - Dwell Start time IS I2 SECONDS ( 0 - 59 ) ] NH3 I2 Start of Second Height Range ( Bin No. ). NH4 I2 End of Second Height Range ( Bin No. ). NHI I2 Height Interval in Bins. NRX B Receiver Bandwidth ( uSec ). DMP B Raw Data Collection Flag. Negative value if Raw Data File Collected. NDW I2 Dwell Number. NCY I2 Cycle Number. MST I2 Run Number. NRS I2 Number right shifts in input data. NXR I4 Record number of next PB. IQ DATA ( IQD ) ----------------------- Inphase (I) and Quadrature (Q) data required for Doppler spectra calculation. This data is stored as sets of 16 compressed integer values. Compression is achieved by only using the number of bits required to store the range of integers in the 16 value set. The first 4 bits of the set give the number of bits minus one used to store each data value. The values are unsigned so that an offset has to subtracted from the number to get the true value. If n is the 4 bit value then the value of the number is :- value - (2^n). Using n+1 bits to extract the value. The data is stored as all the I samples for the first height bin followed by all the Q samples, then the second height bin and so on. Upper height IQ data immediately follows lower height IQ data. BLANK RECORD ( BREC ) ------------------------ EOF 32 * I2 Zeros DATA IN FILE ------------ When data is aquired on the MST Radar system a setup file is used to store the data collection parameters. The radar system uses the information in this setup file to set the radar parameters for each beam before it starts to collect data on that beam. This information is copied to the parameter block for that beam. Data is collected on a given beam direction for long enough to collect all the data points required for the FFT length and FFT bandwidth specified in the setup file. FFT bandwidth is :- 1E6 / (IPI * NPP) ( Hz ). Up to 20 beams may be used when collecting data and the data for each beam is called a Dwell. Data collected for a set of beams is called a Cycle and usually there will be more than one Cycle in an Observation. Therefore each beam collected is labelled with its Dwell and Cycle number. The first height range refers to data collected below 30 Km and the second height range is for data collected above 58 Km. Height of data collected is referenced by range bin which are at intervals of 150 metres. To obtain the true height of a given bin an offset must be subtracted to correct for various time delays in the radar. IQ Data is obtained from the preprocessor data. The preprocessor data consists of two sets of inphase and quadrature data, collected from the two phase detector outputs of the radar receiver, which have been summed over 81.92 mS. If coding was used the first set contains the coded data and the second set the complementary coded data. The aquisition programme decodes this data if coding was used and sums it if not. The data may be right shifted to prevent overflow depending on the pulse repetion interval and length of code used. Additional summing of the data takes place if the FFT bandwidth required is less than 12 Hz, this also may require the data to right shifted. This data, which can now be used to compute the Doppler spectra for the bins collected, is saved in this file as 'raw' data. Doppler spectra are 64,128,256 or 512 points in length and may also be incoherently averaged. The data is stored as I then Q with height for the first time sample followed by I & Q with height for the second time sample and so on until the last time sample. Upper height IQ data immediately follows lower height IQ data. The total amount of IQ data saved for each Dwell is :- 16 * (1 + INT((Lower Bins + Upper Bins - 1) / 16)) Bins. ( i.e. sets of 16 height bins ).
Page maintained by
Last updated 13th January 2005