Metadata database variable list

Occultation Table:

• From instrument software
  • Occluded Satellite -- This is represented by the PRN number, not the SVN number.
  • Receiver channel tracking occulted satellite -- There are eight receiver channels; this information is probably only useful for outage studies
  • Reference Satellite (for double differencing) -- This is represented by the PRN number, not the SVN number.
  • Receiver channel tracking reference satellite -- There are eight receiver channels; this information is probably only useful for outage studies
  • Onboard software (RAMBO) code version -- distinguished by the date the software was compiled
  • Instrument Configuration (see Courtney Duncan's explanation):
    • Occltop -- maximum zoning-line height for HR occs
    • Occlbott -- minimum zoning-line height for MR and HR occs
    • Occlmed -- maximum zoning-line height for MR occs
    • Occlded -- minimum zoning-line height for reference satellites
    • Azimuth -- direction to watch for occultations
    • Occlazs -- Width of field of view
• From satellite telemetry
  • Satellite yaw, roll, and pitch at the time of each occultation
  • Attitude mode -- (see Sandy Alexander's explanation)
• From QCMET
  • Start, end time of occultation -- UTC seconds as determined by beginning and end of data collection. Conversion from GPS time to UTC takes into account leap seconds (as of November 1996 there have been 11 leap seconds since the GPS epoch).
  • Fiducial site used in the calculation -- This number is unique to a particular physical fiducial location -- for example sites POTM and POT2 are both represented by 5, because POTM succeeded POT2 in the same location. FAIR and FAI2 are represented by 9 and 3, respectively, because their physical locations were slightly different.
  • Start latitude and longitude
  • Angular distance of occultation from the day/night terminator -- very approximate calculation where +90 represents an occultation on the spot on earth exactly under the sun; 0 represents an occultation on the day/night terminator, and -90 is exactly opposite the sun.
  • Top altitude of occultation
  • Straight-line approximation (without regard to bending) of bottom altitude of occultation -- because bending is not taken into account, this will often be negative.
  • "smear" - Horizontal change in point of closest approach from top to bottom of inversion
  • Occultation direction (Rising or Setting)
  • Angular elevation of occulted satellite from fiducial site (angle up from ground)
  • Angular elevation of reference satellite from fiducial site (angle up from ground)
  • Azimuth of occultation from LEO -- horizontal angle away from anti-velocity vector (setting occultation) or velocity vector (rising occultation). This is always positive, between 0 and 90 degrees.
  • Azimuth of reference satellite from LEO -- horizontal angle away from anti-velocity vector (setting occultation) or velocity vector (rising occultation). This is always positive, between 0 and 90 degrees.
  • Angular elevation of reference satellite from LEO (angle up/down (+/-) from LEO's local horizontal plane)
  • Zoning line altitude (from horizon) of reference satellite from LEO -- see the explanation of instrument configuration parameters for explanation of "zoning line". A maximum of 40 times the altitude of the LEO satellite is imposed because zoning line altitudes can be arbitrarily high or undefined for high reference satellite elevation angles.
• From Inversion software
  • Subtype and version of the inversion code used -- Information is available on request concerning the difference between different code versions, but for most purposes it should be sufficient to know that the higher the version number, the more recent (and presumably, more perfected) the inversion code.
  • Start and end altitude -- Ideally the start altitude will be 60km, and the end altitude will be 0km. Often the end altitude will be higher because signal lock was lost too soon.
  • Start and end latitude
  • Start and end longitude
  • CASNR, P1SNR, P2SNR -- signal to noise ratio at 40km for CA, P1, and P2, averaged over a 200m range
  • Quality of the inversion in the stratosphere -- A binary value calculated from inversion software output parameters (below): this number is set to 1 if |smean| < 10^-6 and stdv < 3 x 10^-6 and difref < 0.2
  • Quality of the inversion in the troposphere -- A binary value calculated from inversion software output parameters (below): this number is set to 1 if dpmax < 10^-4 and |demax| < 1 and noffset = 0
• From Inversion software -- Output parameters (from explanations by Sergey Sokolovskiy)
  • rfict -- Local radius of curvature of the reference ellipsoid under the tangent point of the last ray for the occultation
  • teralt -- Altitude of terrestrial surface above Mean Sea Level, taken from the ECHAM model.
  • z(nion) -- Altitude in km below which only L1 bending angle is used, corrected for (L1-L2) bending angles. (For higher altitudes, LC excess phase is bigger than "swion".)
  • z(1) -- Maximum altitude for the occultation (km)
  • eimax -- Maximum difference of L1 and L2 benging angles observed above 60 km (indicates ionospheric E-layer when it is considerably bigger than smean and stdv)
  • zimax -- The altitude at which eimax is observed
  • smean -- DC component of bending angle noise -- estimated between 60 and 80 km where combined effect of the neutral atmosphere and ionosphere is minimal. smean is the mean value of
  • stdev -- AC component of bending angle noise -- the standard deviation of
  • scale -- Mean half period of oscillations between 60 and 80 km
  • difref -- Maximal relative devation of retrieved refractivity from the climate model observed between 60 and 80 km (indicates large Level 2 data errors or large atmospheric anomalies)
  • zdifref -- Altitude at which difref (above) is observed (km)
  • dpmax -- Maximum continuous increase of the impact parameter -- indicates quality of bending angle as function of the impact parameter in the lower troposphere
  • demax -- Maximum continuous decrease of the bending angle -- indicates quality of bending angle as function of the impact parameter in the lower troposphere
  • noffset -- Number of data samples cut off using input parameters dpcrt and decrt (above)
  • ifadb -- Set to 1 if adiabatic gradient is exceeded below 60 km; 0 otherwise.
• Variables in Megafiles and Tem files
  • Temperature -- This is dry temperature, i.e. the temperature that we would deduce if we happened to know that there was no moisture in the air. The differences are typically only negligable above 10km where moisture content is negligable.
  • Pressure -- Dry pressure; see the distinction above under Temperature.
  • Latitude
  • Longitude
  • MSL_alt -- altitude above Mean Sea Level
  • Refractivity -- The refractivity measure (N) calculated by the inversion software is related to index of refraction (µ) as follows: N = (µ-1) * 10⁶.
  • Bending Angle
  • Impact Parameter
  • Quality
  • Alpha, Beta, Gamma -- direction cosines of the occultation plane
  • CA SNR
  • P1 SNR
  • P2 SNR
  • LEO X,Y,Z
  • LEO XD,YD,ZD
  • GPS X,Y,Z
  • GPS XD,YD,ZD
  • ExphaseLC
  • ExphaseL1
  • ExphaseL2
  • BendangL1
  • BendangL2
  • Impact_parmL1
  • offset -- The point at which the useful Level 3 data starts
  • shortlen -- The number of good Level 3 data samples
  • Special -- These are the same as the "Output Parameters" listed above, in the same order.