MTP Nomenclature and Abbreviations

MJ Mahoney

Local Links:  A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A
ADR - Air Data Computer. All commercial and research aircraft have an ADR to read aircraft indicators (such as static pressure, pitot pressure, temperature, etc.) and use them to calculate other parameters needed to fly an aircraft (such as Mach Number, pressure altitude and true air speed).

ATP - Altitude Temperature Profile. The variation of temperature with altitude.

AA - Archive Average. The term archive average is used in two contexts. When we calculate a set of retrieval coefficients, we select a group of several hundred radiosondes that have a particular temperature structure from an archive of soundings. The average of this group of soundings is referred to as the archive average temperature profile, or AA temperature profile. When this group of soundings is used to calculate the brightness temperature, or observables, their average values are referred to as the archive average observables, or AA observables.

B
Buttom - A Visual Basic control which when clicked on starts some procedure.

C
Campaign - An organized series of activities designed to obtain a definite result . (see also Mission) From Funk and Wagnall's Standard College Dictionary. I use the terms Mission and Campaign interchangeably.

Check Box - A Visual Basic check box control, which when checked enables some feature of a program.

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F
Frame - A Visual Basic container for related controls.

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Gamma - gamma is the ratio of the specific heats at constant pressure and volume.
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I
ICAO - International Civil Aviation Organization

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M
Mach Number - M. The Mach Number,  Mach No,  is the ratio of the aircraft's true air speed (TAS or va) , and the local velocity of sound vs.  The velocity of sound (to first order, Vs ) depends only on the static air temperature (Ts), where R is the Gas Constant, R , which for dry air is 287.053 J kg-1 K -1 and gamma is the ratio of the specific heats at constant pressure and volume.
Microwave Propagation Model (MPM) -
Originally based on Liebe's model (Liebe, H. J. 1989. MPM – An Atmospheric Millimetre Wave Propagation Model. Int. Journ. Infrared and Millimetre Waves, 10(6): 631-650.) it has had several revisions:
For O2 absorption: 
Submillimeter Line Intensities from HITRAN96. This version differs from Liebe's MPM92 (H.J. Liebe et al, JQSRT V.48, PP.629-643 (1992)) in two significant respects: 1. It uses the modification of the 1- line width temperature dependence recommended by Schwartz: (1/T). 2. It uses the same temperature dependence (X) for submillimeter line widths as in the 60 GHz band: (1/T)**0.8 ( M.J. Schwartz, Ph.D. thesis, M.I.T. (1997))
For H2O vapor:
P.W. Rosenkranz, Radio Science, Vol.33, PP.919-928 (1998).     
For H2O Liquid:
Liebe, Hufford, and Manabe, Int. J. IR & MM Waves, Vol.12, pp.659-675 (1991);  Liebe et al, AGARD Conf. Proc. 542, May 1993.
Revised by Rosenkranz 1998.12.14 for temperature dependence of parameter EPS2 eliminated to agree with MPM93

Mission - Any body of  persons sent someplace in order to perform or accomplish a specific work or service; especially such a body sent to a foreign country to conduct business, negotiations, etc. on behalf of its own country. (see also Campaign) Ffrom Funk and Wagnall's Standard College Dictionary. I use the terms Mission and Campaign interchangeably.

Mission Folder - The folder containing all the data analysis files for a particular mission. For example, for the DC-8 PAVE field campaign, the mission folder would be C:\MTP\Data\DC8\PAVE\

N
NDR - Navigation Data Recorder. All atmospheric research aircraft have a special instrument package to record data needed in real time or post flight to analyze measurements. The MTP for example requires pitch and roll in real time to properly point the scan mirror. Other parameters are also needed to during data analysis. The NDR is generally a different from the air data computer.

NUM File - A file in the mission setup folder which contains the flight number, flight date, and flight objective for each flight in a campaign. For example, the NUM file in the PAVE mission folder (\Setup\PAVE_NUM.txt) looks like this:
050102 20050114 DFRC Test Flight #1
050103 20050118 DFRC Test Flight #2
050104 20050120 DFRC Test Flight #3
050105 20050124 Transit from Dryden FRC to Pease AFB
050106 20050127 1st Local Science Flight - MLS ascending track to Resolute
050107 20050129 2nd Local Science Flight - MLS/TES ascending tracks to north
050108 20050131 3rd Local Science Flight - Deep Vortex Survey
050109 20050203 4th Local Science Flight
050110 20050205 5th Local Science Flight
050111 20050207 6th Local Science Flight
050112 20050209 Transit from Pease AFB to Dryden FRC
The flight number can be just a sequential number, but on some platforms there is a defined structure. For example, a flight number for the DC-8 looks like 050109, which would be the ninth flight on the first campaign of 2005.

O
OAT - Outside Air Temperature. Also called SAT. This is the temperature measured by the aircraft avionics, or by a PI instrument, and is one of the two temperature measurements needed to determine the MTP gain. (The other is the target or reference temperature.) It cannot be assumed that the OAT is always correct, and so careful comparisons must be made against radiosondes near the aircrafts flight track. Not only can there be a bias in the OAT relative to radiosondes, but the bias can be pressure altitude dependent, due, for example, to a pin-hole leak in the static air line.

OATnavCOR - This program parameter stands for a correction (COR) applied to the outside air temperature (OAT) from the navigation data recorder (NDR) or a PI PTW instrument. The OAT measured by aircraft avionics are generally not accurate to 1 K or so, which is not good enough for airborne science. Even PI instrument measurements can have errors as large as 1 K. To determine what the value of OATnavCOR is for a particular field campaign, we make careful comparisons between the measured OAT (Tnav) and the temperature measured by radiosondes that the aircraft flew close to (Traob). OATnavCOR (Traob - Tnav) is ADDED to Tnav to bring Tnav into agreement with radiosondes, which these days have an accuracy of 0.3 K. Typically, OATnavCOR can be determined to an accuracy of <0.2 K if enough comparisons can be made.

Observables - They are the measured brightness temperatures, and possibly other measurements, that are used in a temperature profile retrieval.

P
PI - Principal Investigator. The scientist responsible for data from an instrument.

Pressure Altitude - The altitude based on the US Standard Atmosphere (1976), which relates ambient pressure to altitude using a piecewise continuous model for a mid-latitude temperature profile. It is the altitude scale that airplanes fly on above 18,000 feet in the US. (Below 18,000 feet, barometric altitude is used.)

PTW - Pressure, temperature and wind.

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R

RAOB - Radio Observation performed by a radiosonde.

RCs - Retrieval Coefficients. They are used in a statistical retrieval to convert measured brightness temperature (observables) to a physical temperature profile.

S
SAT - Static Air Temperature. Also called OAT. This is the temperature of the air surrounding the aircraft.

Setup Folder - This folder contain various files needed for different programs involved in data calibration, RC calculation, and data analysis. For example, the Setup files for the PAVE campaign are described below:
PAVE_CAL.txt  -  Default ASCII calibration information
PAVE_NUM.txt  -  Flight numbers, dates, and objectives
PAVE_INI.txt  -  Default ASCII flight information
PAVE_HDR.txt  -  Header information for MP files
PAVE_FDT.txt  -  Final ATP fudge file (not used!)
PAVE_RMS.txt  -  A priori observable errors for RCcalc
PAVE_WCT.txt  -  Window Correction Table
PAVE_FLA.txt  -  Default RC flight altitudes
Until a few years ago, these files would have had names like PAVE.CAL, PAVE.NUM, etc. That's why they were referred to as CAL and NUM files. However, as more of these setup files were created, the extensions often conflicted with extension names used by modern operating systems and other programs. To avoid dealing with these headaches, and because they are all ASCII files, the file extensions were all changed TXT. This also facilitated their being editted by text editors.

Static Air Line - A tube running from a flat port normally on the side of an aircraft (to avoid ram effects) to a pressure transducer in an avionics package.

T
Tab - A tab on a Visual Basic SStab control, which displays a set of related controls and/or containers.

TAT - Total Air Temperature. This is the temperature of the air measured approximately by a temperature probe (such as a Rosemount). It is higher than the static air temperature due to ram pressure, or Mach, heating caused by the motion of the aircraft through the air. I say "approximately" because there are many factors that make the measured temperature slightly different from the true total air temperature. There is a simple relationship between TAT (Tt), SAT (Ts) and Mach Number (M):
Tt_Ts Ratio
where gamma is the ratio of the specific heats at constant pressure and volume. Thus if TAT and M are known, SAT (or OAT) can be calculated. Fortunately, the Mach Number is simply related to the ratio of the total (or ram) pressure (pt) measured by the aircraft's pitot tube, and the static air pressure (ps) measured by the static air line:
Mach Number vs Pt/Ps
A more thorough discussion of the measurement of temperature on an aircraft can be found elsewhere.

Template Profile - A radiosonde temperature profile from a launch site that an MTP flew close to.

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W
Window Correction Table (WCT) - Window corrections are probably a misnomer, but we will use the term in any case because it is so embedded in MTP lore. When the MTP scan mirror moves to different elevation angles, its sidelobes "see" different fairing structure, which introduces small (generally <1 K) brightness temperature offsets.  To correct for these offsets, we compare measured brightness temperatures near radiosonde launch sites to the predicted brightness temperatures calculated assuming that the temperature profile is that of the radiosonde. These comparisons should be done in the stratosphere to avoid errors introduced by aircraft altitude excursions in high lapse rate regions, and at several altitudes. Recently, we have discovered that there seems to be an altitude dependence for the magnitude of the window corrections. One possible explanation for this is that there are errors in the Microwave Propagation Model (MPM) that we use to do the forward radiative transfer calculations. This is still being investigated.

WMO - The World Meteorological Organization based in Geneva, Switzerland.

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