DORIS Data Exchange Format
Version 2.1(January 2002)
Standard Exchange Format for Range-Rate Observations
Columns Subset Description
------- ------ ----------------------------------------------------------
1-7 Satellite identification
8-9 Measurement type
39 = DORIS doppler (up link, on board receiver)
10-11 Time system indicators
10 0 = ground received time
1 = satellite transponder/transmitter time
2 = ground transmitted time
3 = satellite received time
11 5 = TAI
12-16 Station ID
Fourth letter indicates Alcatel(A) or Starec(B)antenna
17-32 Time observation (beginning of count)
17-18 Time of observation (beginning of count)
Year minus 1900 if greater than 90
Year minus 2000 if less than or equal 90
19-21 Day of year (January 1 = Day 1)
22-26 Seconds from midnight
27-32 Fractional part of seconds (microseconds)
33-35 Preprocessing indicators
33 0 = ionosphere correction applied
1 = ionosphere correction not applied
34 0 = troposphere correction applied
1 = troposphere correction not applied
35 0 = point considered to be good
1 = point edited during pre-processing
2 = point edited during post-processing
36-45 Count interval in 0.1 microseconds
46-56 Range rate in micrometers/second
57-66 Meteorological data
57-60 Surface pressure (millibars)
61-63 Surface temperature (degrees kelvin)
64-66 Relative humidity (percent)
67-72 Observation standard deviation (micrometers/second)
73-80 Ionospheric refraction correction (micrometers/second)
81-87 Tropospheric refraction correction (micrometers/second)
88-90 Meteorological data source, beacon type
88 Beacon type
1 = permanent network
2 = field experiment
3 = others
89 Meteorological data source
0 = measured parameter
1 = pressure from a model
3 = temperature from a model
4 = pressure and temperature from a model
5 = humidity from a model
6 = pressure and humidity from a model
8 = temperature and humidity from a model
9 = pressure, temperature, and humidity from a model
90 Channel indicator (1, 2, etc.)
91-96 Center of mass correction (micrometers/second) including
both effects: satellite and beacon
Specifications on the DORIS data format:
Time for DORIS = beginning of count interval
Range rate has been computed using the following equation:
V(r) = c/f(bea)[(f(bea)-f(sat))-D/dt]
= [c/f(bea)][f(bea)-f(sat)] + [c/f(bea)][-D/dt] (1)
with V(r) = range rate (m/s)
dt = count interval (s)
D = cycle count
c = 299792458 m/s
f(bea)= nominal beacon frequency (change from Version 1)
f(sat)= best estimate of the actual satellite frequency after
long term on-board frequency drift taken into account
(no relativity correction has been applied)
Because the true frequency offset between f(bea) and f(sat) will be
slightly different from the nominal value, a bias is typically
estimated for each station pass.
The corresponding processing equation for Version 2.1 data is
V(r) = c(df(bea)/fbea - df(sat)/fsat) + c[{1 + df(bea)}/f(bea)][-D/dt] (2)
= bias + [c/f(bea)][-D/dt] + df(bea)[c/f(bea)][-D/dt]
where df(bea)= difference between actual beacon frequency and the
nominal value used to generate the data
df(sat)= difference between actual satellite frequency and
the best available estimate used to generate the data
Important note for Version 2.1 processing: Previous to Version 2.1, the
beacon frequency was the best available estimate of the actual frequency.
In Version 2.1, the nominal value of the beacon frequency is used instead.
For beacons where the offset between the actual and nominal frequency is
large, the last term in Eq. 2 may not be insignificant. It is recommended
that the df(bea) term be explicitly included in the processing, where
the quantity df(bea) is determined from the pass bias estimate. Since
df(sat) will usually be small, the pass bias estimate will mainly
reflect the beacon frequency offset. This value can be used to improve
the measurement model by the addition of the term (add to the computed
range-rate or subtract from the observed range-rate)
df(bea)[c/f(bea)][-D/dt]
where df(bea) is inferred from the pass bias and (c/f(bea)(-D/dt) is
simply the range-change over the count interal dt. When df(bea) is
small, as in the case of Version 1 DORIS data, this term will have no
significant effect. It is only when df(bea) is large that a range-rate
dependent error is encountered.
All corrections (ionosphere, troposphere, and center of mass) should be
added to observed values or subtracted from computed values