Data Set Summary ================ Data Set ID: ULY-J-URAP-4-SUMM-RAR-AVG-E-144S-V1.0 Instrument: URAP Radio Astronomy Receiver (RAR) Instrument P.I.: Robert J. MacDowall Data Supplier: Roger Hess Data sampling rate: 144 seconds Data Set Start time: 1992-01-01T00:00:00.000Z Data Set Stop time: 1992-04-30T23:57:36.000Z Naming convention ----------------- Data files in this data set are named according to the convention: Tyymmdd.TAB where yy = the last two digits of the year ('92' for 1992) mm = the month of year dd = the day of month covered in the file Record format ------------- These files can be read according to the FORTRAN format statement: '(a24,5(1x,i1),75(1x,1pe11.4))' where 'a24' is the time stamp in PDS format: yyyy-mm-ddThh:mm:ss.sssZ. The individual elements of the time field can be read according to the statement: '(i4,4(1x,i2),1x,f6.3,1x)' year, month, day, hour, minute, seconds. thus a record may be alternatively be read according to the format: '(i4,4(1x,i2),1x,f6.3,1x,5(1x,i1),75(1x,1pe11.4))' Data column descriptions ------------------------ time a24 spacecraft event time in format yyyy-mm-ddThh:mm:ss.sssZ lopolmod i1 Polarization mode of the low receiver band. Their values are defined as: 1: Polarization on. 2: Polarization off. 3: Polarization mode switched during the averaging interval. 4: Polarization mode was unknown (usually due to a data gap). losummod i1 Polarization mode of the low receiver band. Their values are defined as: 1: Summation on. 2: Summation off. 3: Summation mode switched during the averaging interval. 4: Summation mode was unknown (usually due to a data gap). hipolmod i1 Polarization mode of the high receiver band. Their values are defined as: 1: Polarization on. 2: Polarization off. 3: Polarization mode switched during the averaging interval. 4: Polarization mode was unknown (usually due to a data gap). hisummod i1 Polarization mode of the high receiver band. Their values are defined as: 1: Summation on. 2: Summation off. 3: Summation mode switched during the averaging interval. 4: Summation mode was unknown (usually due to a data gap). bps i1 BPS indicates the telemetry bit rate during the averaging interval. Its values are defined as: 1: 128 bps. 2: 256 bps. 3: 512 bps. 4: 1024 bps. 5: Bit rate changed during the averaging period. 6: Bit rate unknown - usually due to a data gap. rar avg e-field -- 76 1pe11.4 format Radio Astronomy Receiver (RAR) electric field averages (over 144 second intervals). F is a vector containing the average signal for the 76 frequencies of the low and high bands. Elements 0 through 63 are from the low band receiver and correspond to frequencies of 1.25+0.75*N KHz where N is the element number (0..63). The frequency channels from 64 to 75 correspond to the following frequencies: F(64): 52 KHz F(65): 63 KHz F(66): 71 KHz F(67): 100 KHz F(68): 120 KHz F(69): 148 KHz F(70): 196 KHz F(71): 272 KHz F(72): 387 KHz F(73): 540 KHz F(74): 740 KHz F(75): 940 KHz Missing data flag value ----------------------- Any data column whose value is -9.999e+10 is a missing data value. Data Description ================ GUIDE TO THE ARCHIVING OF ULYSSES RADIO AND PLASMA WAVE DATA Roger Hess, Robert MacDowall, Denise Lengyel-Frey March 15, 1995 Contents 1 Introduction 3 2 Delivery Schedule 3 3 Description of the Unified Radio and Plasma Wave Instrument 4 3.1 Radio Astronomy Receiver 4 4 World Wide Web Access to URAP Data 7 APPENDICES 8 A UDS data files 8 A.1 Radio Astronomy Receiver 8 C USER'S GUIDE TO RAR 144 SECOND AVERAGED DATA FILES 21 1 Introduction The Unified Radio and Plasma wave instrument (URAP) is designed to detect both remotely-generated electromagnetic waves and in-situ plasma waves. The former are radio waves arising from electron beams in the solar wind (type II and type III radio bursts), planetary radio emissions (from Jupiter, the Earth, etc.), and a cosmic background from the local galactic medium. The in-situ waves include thermal plasma fluctuations, electron plasma oscillations (Langmuir waves), ion-acoustic waves, and whistler-mode waves. Wave electric fields from less than 1 Hz to 940 kHz and magnetic fields from less than 1 Hz to 448 Hz can be measured. An extensive description of the five instruments that make up the URAP investigation can be found in [STONEETAL1992A]. Details relevant to the data archive are contained below. The Astron. Astrophys. Suppl. Ser. issue also contains other articles describing the Ulysses spacecraft as a whole and the other Ulysses instruments. Ulysses is spun for stability with a period of approximately 12 sec. The Z axis of the spacecraft is defined as being along the spin axis. The X and Y axes are perpendicular to the spin axis. URAP measures electric field by means of two antennas. One is a dipole formed by two 35 meter long wires along the +/- X axes and the other is a 7.5 meter long monopole that is on the Z axis Because of the longer length of the X antenna compared to the Z antenna, it is much more sensitive and has a much lower background signal level. For these reasons, only the X antenna data are provided in the UDS data files. Magnetic fields are measured by means of a two axis sensor aligned along the spacecraft Y and Z axes. 2 Delivery Schedule The URAP team will provide the archival data products to the Ulysses Data System no later than 2 months after GSFC has received the raw data. These data will be provided to the NSSDC no later than 1 year after GSFC has received the raw data. 3 Description of the Unified Radio and Plasma Wave Instrument The Unified Radio and Plasma Wave instrument on Ulysses is divided into several sub-instruments. Data from three of these sub-instruments, the Radio Astronomy Receiver, the Plasma Frequency Receiver, and the Wave Form Analyzer, are represented in the URAP archival data. 3.1 Radio Astronomy Receiver The Radio Astronomy Receiver is divided into two parts, a low frequency receiver and a high frequency receiver. The low frequency receiver has 64 channels that cover the frequency range from 1.25 to 48.0 kHz in linear steps of 0.75 kHz. The high frequency receiver has 12 channels that cover the range from 52 kHz to 940 kHz in approximately logarithmic steps. The high frequency receiver is usually operated in what is called "measure" mode, which causes the receiver to step repeatedly through a list of frequencies that is determined by a ROM on board the spacecraft. There are 16 different lists and one of them is chosen by telecommand. The different lists emphasize different frequency ranges, so as to maximize the information received depending on the type of phenomena being studied. Some of the lists include all 12 possible frequency channels while other lists skip some of the frequencies. The list that has been used for most of the mission does include all frequecies, but there may be times when other lists have been used. At these times only a subset of the frequencies will be present. The low frequency receiver can be operated in measure mode (with its own set of lists of 8 or 16 frequencies) or in "linear sweep" mode where it steps through a contiguous set of frequencies. In linear mode, all 64 frequencies can be stepped through, or a subset of 32 frequencies can be chosen using the lower half, middle half, or upper half of the frequencies. For most of the mission, the low frequency receiver has been operated in linear mode with all 64 frequencies but there have been periods when it has operated in measure mode or in in linear mode with less than 64 frequencies. During these periods only a subset (8, 16, or 32) of the 64 possible frequencies will appear. Besides the intensity of a signal reaching the spacecraft, the RAR can also, when operated in particular modes, determine additional information about the source of the radiation, including its direction relative to the location of Ulysses, its angular size, and its polarization. This is most efficiently done with the signal from the X and Z axis antennas summed together electronically either with or without a phase shift added between the two signals. Although this additional information cannot be recovered from the averaged data, the mode does have a large effect on the background signal level, so the mode of high and low frequency receivers is given in the data as either summed (X and Z antenna combined) or separate (X antenna alone). 4 World Wide Web Access to URAP Data Some of the URAP data are being made available over the World Wide Web (WWW). By this means, the data are made convenient and quick to use by a much larger audience, including anyone with access to the Internet. The URAP home page on the WWW provides more information for those interested. The home page makes available color dynamic spectra of the RAR data and information on the location of Ulysses during the mission. Educational material and a bibliography of papers describing Ulysses and URAP are also provided. The home page also gives links to other WWW sites of interest including NASA, Goddard Space Flight Center, the Jet Propulsion Laboratory and the European Space Agency, as well as other investigators using the Ulysses instruments and data. The Universal Resource Locater for the URAP home page is http://urap.gsfc.nasa.gov/www.urap_homepage.html APPENDICES A UDS data files Eight files are provided that conform to the UDS conventions regarding the naming of files and the format of the data. The eight files are divided into 4 pairs of files with each pair consisting of a file containing data averaged over a 10 minute period and a file containing the maximum data value during the same 10 minute period. The 4 pairs of file contain data for the RAR, the PFR, WFA - magnetic field, and WFA - magnetic field. The names of the files are (following the UDS convention): Tyyddmm.TAB : Average data where: yy = Last two digits of year. mm = Month of year (01...12). dd = Day of month (01...31). C USER'S GUIDE TO RAR 144 SECOND AVERAGED DATA FILES This document describes the contents and format of the RAR 144 second averaged data files. The time period of 144 seconds was used for the averaging period because that is the basic cycling time of the instrument. The RAR continually cycles through a list of frequencies. There are 16 lists and the list currently in use is chosen by telecommand. The time period to complete the list is 144 seconds for the high band of the receiver (for telemetry bit rates of 1024 and 512 bps, the cycle time is 64 seconds for bit rates of 256 and 128 bps), after which the instrument begins with the list again. Therefore this period was chosen for the averaging period. The format of the data is indicated by the following Fortran statement which can be used to read the data: DIMENSION F(0:75) READ(1,'(I4,4(1X,I2),1X,F6.3,5(1X,I1),75(1X,1PE11.4))') + IYEAR, IMONTH, IDAY, IHOUR, IMINUTE, SECOND, + LO_POL_MODE, LO_SUM_MODE, HI_POL_MODE, HI_SUM_MODE, + IBPS, F The variables are defined as follows: The date and time of the beginning of the averaging period is given in TIME in the format yyyy-mm-ddThh:mm:ss.sssZ. LO_POL_MODE and HI_POL_MODE are the polarization modes of the low and high receiver bands. Their values are defined as: 1: Polarization on. 2: Polarization off. 3: Polarization mode switched during the averaging interval. 4: Polarization mode was unknown (usually due to a data gap). LO_SUM_MODE and HI_SUM_MODE are the polarization modes of the low and high receiver bands. Their values are defined as: 1: Summation on. 2: Summation off. 3: Summation mode switched during the averaging interval. 4: Summation mode was unknown (usually due to a data gap). IBPS indicates the telemetry bit rate during the averaging interval. Its values are defined as: 1: 128 bps. 2: 256 bps. 3: 512 bps. 4: 1024 bps. 5: Bit rate changed during the averaging period. 6: Bit rate unknown - usually due to a data gap. F is a vector containing the average signal for the 76 frequencies of the low and high bands. Elements 0 through 63 are from the low band receiver and correspond to frequencies of 1.25+0.75*N Khz where N is the element number (0..63). The frequency channels from 64 to 75 correspond to the following frequencies: F(64): 52 KHz F(65): 63 KHz F(66): 71 KHz F(67): 100 KHz F(68): 120 KHz F(69): 148 KHz F(70): 196 KHz F(71): 272 KHz F(72): 387 KHz F(73): 540 KHz F(74): 740 KHz F(75): 940 KHz The units of the data are microvolt/Hz**.5 measured at the receiver input terminals. To convert to electric field strength the given data must be divided by the effective length of the antenna. This is complicated by the fact that the effective length depends on the antenna impedance which is affected by the plasma conditions local to the Ulysses spacecraft. The impedance will also depend on the frequency. In general, the RAR frequency channels that are well above the local electron plasma frequency are not affected by the plasma conditions and the effective length of 23 meters can be used. When the RAR is in summed, rather than separate, mode the determination of field strengths is even more difficult.