WARNING: Version-2 MST radar data products are DEPRECATED
Users are encouraged to make use of version-3 radial files.
Click here to find out about
earlier versions of the signal processing.
These files contain radial (i.e. along-beam) profiles of the radar
return parameters (noise power, signal power, Doppler shift and
spectral width) for different beam pointing directions.
Data are recorded at 150 m intervals in range and
cover the approximate range 2 - 20 (for the ST mode) or 58 - 96 km
(for the M mode). For most purposes the Cartesian data will suffice
and it should only be necessary to examine the radial data for
Click here to find out about the
contents of other files.
File naming convention:
||is a 4-digit year [1990 - ]
||is a 2-digit month [01 - 12]
||is a 2-digit day [01 - 31]
||is the altitude mode ['st': approximately 2 - 20 km | 'm': approximately 58 - 96 km]
||is the range resolution (m) [150 | 300 | 600 |
1200 | 2400 | 4800]
contains 300 m resolution radial data over the ST altitude
range for 1st January 2005.
Click here for the background to the
file naming convention.
File location: /badc/mst/data/mst-products-v2/radial/
Click here for the location of other files.
Archiving convention: YYYY/MM
Click here for a further explanation.
Data availability: refer to Instrument
(ASCII) NASA-Ames files, with a File Format Index of 2110, are used, i.e. the
same as for Version-1 data
products. However, there are some small differences in the file
contents. Users will therefore need to make a few modifications to any
software designed for dealing with Version-1 products.
Only those aspects of the file format which are essential for reading
the data will be described. For a full description of the NASA-Ames
formats, consult the Gaines
and Hipskind  document.
The radial file for 1st January 2005 will be used as an example. Text
in green represents actual file contents. Text in red is for
explanatory purposes only.
- Line 1: 88 2110
Integer 1 corresponds to the total number of header lines,
Integer 2 corresponds to the File Format Index
- Line 7: 2005 01 01 2005 01 10
Integers 1 - 3 correspond to the year, month and day on which the observations were made.
Integers 4 - 6 correspond to the year, month and day on which the
file was created.
- Line 11: 6
The number of primary variables, nr_primary_vars.
- Line 13: 999.99 999.99 999.999
99.999 999 99999
Missing data values, in order, for the nr_primary_vars primary variables listed below. Greater use is made of missing
data values than in the Version-1 files and so users should make
sure that they make the appropriate substitutions when they read
in the data.
- Lines 14 - 19:
The names of the primary variables (listed below).
- Line 20: 16
The number of auxilliary variables, nr_aux_vars).
- Lines 23 - 38:
The names of the nr_aux_vars auxilliary variables (listed below).
- Line 45: 130 3660 1
Integer 1 corresponds to the number of range gates per dwell, nr_range_gates,
Integer 2 corresponds to the total number of dwells, total_nr_dwells, and
Integer 3 corresponds to the number of different cycle formats,
which is typically (but not always) equal to 1.
- Lines 58 - 86:
Global data attributes following the netCDF CF 1.0
convention. This includes a processing history. It is not
necessary to know this information in order to read the file.
Data reading loop
After reading the above mentioned lines, wind forward to line (nr_header_lines + 1) where the data
begin. Associated with each dwell of observation there is a single
line of auxiliary variables followed by nr_gates lines of primary variables. The data
can therefore be read with a simple loop structure of the form (shown
here in Fortran syntax):
do total_dwell_nr = 1,total_nr_dwells
do gate_nr = 1,nr_gates
Reading auxiliary variables
Each auxiliary variables line contains the second independent variable
(dwell time) followed by the 16 auxilliary variables (a mixture of floating
point, F, and integer, I values), shown here for the
first dwell in the file:
116 130 1 1 1 11 27.7 6.0 8 2 2 320 18
147 512 128 1
Reading primary variables
- Value 1: Cycle time (s) I
Technically speaking this is the second independent variable
rather than an auxiliary variable. The time is given in seconds
since 00:00:00 UTC for the day in question.
- Value 2: Number of range gates I
This is the same as nr_gates given in
line 45 of the header and so can be ignored.
- Value 3: Cycle number I
- Value 4: Cycle format number I
- Value 5: Dwell number (within current cycle)
which is different from total_dwell_nr
(except for the first cycle).
- Value 6: Beam pointing number I
which ranges between 0 and 16. The same information is contained within
the next 2 auxilliary variables. Follow
this link to see the relationship between beam number and beam
- Value 7: Beam pointing azimuth (degrees clockwise from North)
which can have values of 0.0° (for a vertically directed beam only),
27.5°, 72.5°, 117.5°, 162.5°, 207.5°, 252.5°,
297.5° or 342.5°.
- Value 8: Beam pointing zenith angle (degrees from vertical)
which can have values of 0.0°, 4.2°, 6.0°, 8.5° or
- Value 9: Transmitter pulse length (μs)
which can have values of 1, 2, 4, 8, 16 or 32 μs.
- Value 10: Transmitter sub-pulse length (μs) I
which can have values of 1, 2, or 4
μs, for pulse lengths of 4 μs and longer for which pulse
coding has been used. If the sub-pulse length is equal to the
pulse length, then no pulse coding has been used.
- Value 11: Receiver bandwidth (μs) I
this is equal to the transmitter sub-pulse
length, or to the pulse length if no pulse coding has been used, and
determines the range resolution (values shown in brackets). Possible
values are 1 μs (150 m), 2 μs (300 m), 4 μs (600 m), 8 μs
(1200 m), 16 μs (2400 m) and 32 μs (4800 m). This value is the
same for all dwells within a single file.
- Value 12: Inter-pulse period (μs)
This determines the maximum unambiguous range from which radar returns
can be received (values in brackets). It can have values of 80 μs
(12 km), 160 μs (24 km), 320 μs (48 km) and 640 μs (96 km).
- Value 13: Bottom range gate number I
The bottom and top (next value)
range gate numbers are given for reference only. The total number
number of range gates was already given in value 2 and the range
of each gate from the radar is shown in the first column of data
for each dwell.
- Value 14: Top range gate number I
See value 13.
- Value 15: Number of coherent integrations I
This is the number of raw radar samples averaged.
- Value 16: Discrete Fourier transform length I
This is the number of (averaged) samples from which a Doppler power
spectrum is derived.
- Value 17: Number of incoherent integrations I
This is the number of Doppler power spectra averaged together before
the principal spectral parameters are evaluated.
These lines contain 7 values: the first independent variable (range
from the radar) followed by the 6 primary variables, as shown below
for the first line of the first cycle. These are a mixture of floating
point, F, and integer, I values.
1645.0 41.98 59.23 0.176 0.510 32 32799
- Value 1: Range from the radar (m)
Technically speaking this is the first independent variable rather
than a primary variable. The same range gate grid is used for all
dwells within the file and so only needs to be saved once. The
range is given in metres away from the radar, which is at 50 m
above mean sea level.
- Value 2: Spectral noise power (dB)
The noise power is included for reference and is not typically used
as a parameter in its own right.
- Value 3: Radar return signal power (dB)
P_dB = 10 × log10[P_linear]
- Value 4: Radial air velocity (m/s)
Positive values imply motion AWAY from the radar.
- Value 5: Radar return spectral width (m/s)
This corresponds to an e-1/2 half-width. Follow
this link for further information.
- Value 6: Peak power spectral density (PSD) relative to the mean noise PSD (dB) I
This is used for reliability flagging. Signals with a value of greater
than 10 dB are typically clearly distinguishable above the background
noise. Signals with values of less than 10 dB might still be reliable
but should be treated with caution.
- Value 7: Reliability flag
Note that this uses a different convention to that used for the
reliability flags in the Version-1 files. A larger
range of information is now stored bit-wise in a 16-bit integer,
with the 15th bit being used as an overall indicator of data
reliability. Therefore data may be regarded as reliable
flag value >=
The convention has been adopted so that more pieces of information can
be added to the flag value at a later date, without changing the
acceptance condition. At present, only 6 of the available 16 bits are
The threshold values used for a particular file are quoted in header
lines 52 - 56.
||peak signal PSD to noise PSD >= threshold value
||time continuity threshold exceded
||complementary beams are available
||complementary beam factor >= threshold value
||complementary beam factor is significant
||overall reliability flag
- Return to the top of the page
- Gaining access to the data
- File naming convention
- Data archiving convention
- Data locations
- The differences between
signal processing versions
- The contents of other data files
description of the NASA-Ames formats: Gaines and Hipskind