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4DDA: Four Dimensional Data Assimilation

ACS: Attitude Control System - System, including ACE, sensors, actuators, etc. that are used to sense and control spacecraft attitude.

ARL: Applied Research Laboratory, University of Texas

Ancillary: supplementary, auxilliary; see ancillary met

Ancillary Met: Correlative data from other meteorological models and measurements, collected for the purpose of comparison with GPS/MET data. (Also referred to as "correlative data".)

A/S: Anti-Spoofing; a mode that the GPS satellites are usually in, which degrades the accuracy of pseudorange and carrier phase on the L2 signal.

Attitude: The satellite's physical orientation; i.e. which way it's pointing relative to the orbit plane.

Azimuth: Angular direction left or right of a reference point or line

Beta angle: The angle between the plane of the spacecraft's orbit, and the line connecting the centers of the Earth with the Sun. The beta angle partially determines the attitude mode, which in turn governs the amount of power the spacecraft has and the quality of the GPS/MET occultation data.

BUFR: Binary Universal Form for the Representation of Meteorological Data. A WMO standard data format for weather observations.

CDAAC: The COSMIC Data Analysis and Archive Center. A computer center used for rapid processing of COSMIC data and distribution of same to researchers and operational centers worldwide.

CDDIS: Crustal Dynamics Data Information System

CERTO/TBB: Coherent Electromagnetic Radio Tomography / Tri-Band Beacon (satellite transmitters for probing the ionosphere)

CG: center of gravity

COSMIC: Constellation Observing System for Meteorology, Ionosphere and Climate

CVS: Concurrent Version System

Colatitude: 90 - latitude

DCB: Differential Code Bias

Double Differencing: Data processing technique that combines measurements from four links to elminate most clock and Selective Availability errors.

EGM96: Earth Gravity Model - 1996.Lemoine et al., 1998.

ECMWF: European Center for Medium Range Weather Forecasting.

Elevation: When looking at the sky, "elevation" represents an angle to a satellite up or down from the local horizon.

Ephemeris: A table showing a satellite's location over time.

FC: The satellite's onboard Flight Computer

FC Reset: Flight Computer Reset -- sometimes the Microlab-1 Flight Computer resets itself, and sometimes it is reset by OSC; in either case it may lead to a gap in GPS/MET data if recovery commands are not sent immediately afterwards.

Fiducial: Fiducial sites are fixed GPS receivers on the ground, against which data from the satellite can be differenced. GPS/MET uses data from six sites which take measurements once per second.

FORMOSAT-3 : Formosa Satellite Mission #3. A series of satellites launched by Taiwan. Name of the COSMIC mission in Taiwan.

GIM: Global Ionospheric Map

GPS: Global Positioning System

GPS/MET: Global Positioning System/Meteorology

GTS: Global Telecommunication System

HR: High Rate. Used for data taken at a rate of 50 observations per second; these are used for measurement of the stratosphere and troposphere

HSFE: High Speed Front End - Part of the equipment at the ground station which receives downloaded information

IGS: International GPS Service for Geodynamics; a network of GPS receiver sites, the data from which precise orbits are calculated.

JPL: The Jet Propulsion Laboratory

L1: GPS carrier frequency, 1575.42 MHz

L2: GPS carrier frequency, 1227.60 MHz

LEO: Low Earth Orbit

Latch Up: A serious error in the satellite's onboard computer caused by solar radiation.

Level 0: Raw data as collected by the orbital equipment, and stored at the CDAAC

Level 1: Data from the satellite and the fiducial sites, put in more manageable files.

Level 2: Precise orbits for the Microlab and GPS satellites, and excess phase profiles for each occultation >

Level 3: Various atmospheric and ionospheric products

LOS: line-of-site

LR: Low Rate data; observations taken once every ten seconds, used to calculate the satellite's orbit.

Megafile: Data file containing both excess phase information and the refractivity, pressure, and temperature profiles derived from them.

Met: meteorological

Microlab-1: The satellite containing the GPS/MET instrument.

MR: Medium Rate data; observations taken once per second, used to study the ionosphere.

NCAR: National Center for Atmospheric Research, a division of UCAR

NESDIS: NOAA's National Environmental Satellite, Data, and Information Service

NMC/NCEP: National Meteorological Center / National Center for Environmental Prediction

NRL: Naval Research Laboratory

NSC: National Science Council of Taiwan

NSF: National Science Foundation

NSPO: Taiwan National Space Program Office

Occultation: Every time the earth comes between the LEO satellite and a GPS satellite, the GPS satellite appears to be "occulted" or hidden from view. Each time this happens, one set of measurements can be taken, of conditions in the atmosphere at the precise point on the earth's surface where the GPS satellite appears to be setting.

Occultation parameters: The software settings on the instrument that govern its choice of occultations to observe.

OSC: Orbital Sciences Corporation; the operators of the Microlab-1 satellite.

OSSE: Observing Systems Simulation Experiment -- In this methodology, a weather simulation model is used to generate simulated observations, for input to a separate weather prediction model. The forecast of the prediction model is then compared to the later state of the weather simulation. By using different types of observations to run the prediction model, the usefulness of different observation techniques can be compared.

PI: Principal Investigator

Pitch: Nosing up or down, with respect to direction of motion; see also yaw and roll.

POD: Precise Orbit Determination -- The precise location and velocity of the satellite at a given time can be deduced after the fact from GPS measurements made by the satellite and by ground-based IGS stations.

PRN: Pseudo-Random Noise -- one of 32 possible "gold codes" assigned to each GPS satellite; the PRN number is used in this database to identify different GPS satellites.

RINEX: Receiver Independent Exchange Format; a standard file format for storing the observations of GPS receivers.

Roll: Rotation about the axis of motion; see also yaw and pitch

Rx: receiver

S/A: Selective Availability; a mode that the GPS satellites are usually in, which degrades the accuracy of their signal for non-military users

S/C: Abbreviation for "spacecraft" -- specifically the Microlab-1 satellite

SNR: Signal to Noise Ratio

SOC: state of charge

SOH: state of health

SOCC: Satellite Operations Control Center

State Vector: A collection of variables that can be uploaded to the satellite to set its state.

SVN: Identification number assigned to each GPS satellite

T1: Telephone company terminology for a specific type of high-bandwidth phone line; in Microlab status reports the term refers specifically to the link between the RTS (where data is downloaded from the satellite) and the SOCC (Spacecraft Operations Control Center).

TACC: Taiwan Analysis Center for COSMIC

TBB: Tri-Band Beacon

TEC: Total Electron Content

TECU: 1 TECU = 1e16 electrons/meter/meter

TIP: Tiny Ionospheric Photometer

UCAR: University Corporation for Atmospheric Research

UNAVCO: University Navstar Consortium

U.S.: United States

UTC: Coordinated Universal Time

Yaw: Rotation to the left or right, with respect to direction of motion; see also pitch and roll

WMO: World Meteorological Organization