PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT PUBLICATION_DATE = 2002-09-16 NOTE = "INFO.TXT describes the Electron Reflectometer (ER) data available on this volume." END_OBJECT = TEXT END The DATA/ER directory contains the Electron Reflectometer (ER) data. These data consist of a time ordered series of omnidirectional electron flux measurements from the Electron Reflectometer instrument on the Mars Global Surveyor (MGS) spacecraft. The ER data on this disk cover the period 2/20/02 - 3/5/02. Within an ER data file, each record consists of a time tag with 19 scalar data points representing measurements of the electron flux in 19 different energy channels, ranging from about 10 eV to 20 keV, with an energy resolution of 25%. Each data point is a measure of the electron flux (cm-2 sec-1 ster-1 eV-1) averaged over a 360 x 14 degree disk-shaped field of view (FOV). (Parts of this FOV are masked because of spacecraft obstructions.) During the Science Phasing Orbits (SPO), the spacecraft was in Array Normal Spin (ANS) configuration, for which the ER field of view sweeps out the entire sky (4-pi ster) every 50 minutes, which is much longer than the integration time per record (2 to 48 sec, depending on energy and telemetry rate) and much longer than most timescales of interest in Mars' plasma environment. The ER data are intended to be used in conjunction with the Mars Global Surveyor Magnetometer (MAG) data, which provide the magnetic field vector and spacecraft ephemeris data as a function of time. Electrons travel along the magnetic field lines in tight helices (few km radius) at high speed (roughly one Mars diameter per second). Thus the electron data contain information about the plasma environment, as well as about the large-scale configuration of the magnetic field, which is sampled locally by the MAG. (The MAG data are found in the directory /DATA/MAG on this disk.) The file naming convention for files in the DATA/ER directory is as follows: 99067.STS is interpreted as 99 = year 1999 067= day of year '067' STS= 'standard time series' format The detached PDS label file describing the file 99067.STS is named 99067.LBL. Each ER data file consists of an attached ASCII text header, followed by an ASCII table containing 1 day of time series data. The table in each file has fixed-length records of length 233 bytes. Each row of data contains 20 columns, and is terminated by the ASCII record delimiter characters carriage return and line feed. Each row consists of a time stamp followed by 19 electron flux values. The data are provided at the full instrument downlink sampling frequency, which varies by orbit (spacecraft telemetry mode). In addition to the data files, this disk contains documentation files which describe the datasets on the disk, the instruments from which the data came, and the Mars Global Surveyor spacecraft and mission. These files are found in the CATALOG and DOCUMENT directories, and are described in the files CATALOG/CATINFO.TXT and DOCUMENT/DOCINFO.TXT. This disk also contains browse plots (PostScript files) summarizing the ER and Magnetometer (MAG) data on the disk. These plots are contained in subdirectories of the BROWSE directory. Besides accessing ER data files directly, users with Web browsers can access them via links in the HTML file ERDATA.HTM in the EXTRAS directory. Such users also can navigate the entire disk using the file AAREADME.HTM in the disk root directory.