'The ISEE-1 and -2 Plasma Wave Investigation' D. A. Gurnett, F. L. Scarf, R. W. Fredricks, and E. J. Smith, IEEE Transactions on Geoscience Electronics, Vol. GE-16, p. 225-230, 1978. The International Sun-Earth Explorer (ISEE) Program consisted of three satellites intended to study the Earth's magnetosphere and the solar wind. ISEE-1 and ISEE-2 were launched on October 22, 1977 into highly elliptical geocentric orbits. The satellites passed through the magnetosphere and into the magnetosheath during each orbit. ISEE-3 was launched on August 12, 1978 and subsequently inserted into a 'halo orbit' about the the libration point situated about 240 earth radii (Re) upstream between the earth and the sun. Plasma passing this point arrives at the Earth about one hour later where it may cause changes that can be observed by ISEE 1 and ISEE-2. These two spacecraft, separated by a variable distance and with similar instrument complements, were intended to resolve the space-time ambiguity associated with measurements by a single spacecraft on thin boundaries which may be in motion such as the bow shock and the magnetopause. ISEE-1 and ISEE-3 were the principal U. S. contributions to the International Magnetospheric Study. ISEE-2 was built and managed by the European Space Agency. In September 1982 ISEE-3 was diverted from its 'halo orbit' to explore the earth's deep tail region through much of 1983 on its way to an encounter with the comet Giacobini Zinner in September 1985. ISEE-1 had a complement of thirteen experiments to measure the waves, fields, plasma, and particles. The University of Iowa Plasma Wave Instrument (PWI) was one of these thirteen. The ISEE-1 plasma waves instrument provided a comprehensive determination of wave characteristics over a broad frequency range, including high-frequency resolution spectrum scans, simultaneous high-time resolution electric and magnetic frequency spectrum measurements, wave normal and Poynting flux measurements, and wide-band waveform measurements. PWI sampled the environment using three electric dipole antennas with lengths of 215, 73.5, and 0.61 meters for electric-field measurements, and a triaxial search coil antenna with three 16-in high permeability mu-metal cores each wound with 10,000 turns of wire and a preamplifier for magnetic-field measurements. The experiment's main electronics consisted of four main elements: 1) a narrow-band sweep frequency receiver, 2) a pair of high time resolution spectrum analyzers, 3) a wave normal analyzer, and 4) an analog waveform receiver (also called a wide-band receiver). These elements could be electrically connected to the six antennas in various combinations in flight. Data for this file originate with an electric antenna and were measured via the Sweep Frequency Receiver (SFR). The narrow-band sweep frequency receiver was intended to provide very high resolution spectrums with low time resolution for analyzing relatively steady narrow- band emissions such as upper hybrid resonance noise, electron plasma oscillations, and electron cyclotron harmonics. The receiver has 32 frequency steps in each of four bands covering the frequency range from approximately 100 Hz to 400 kHz. The frequency steps are logarithmically spaced with a frequency resolution of about 6.5 percent of the center frequency. The dynamic range of the receiver is 100 dB in the lowest three frequency bands, and 80 dB in the highest. Because the time resolution of the SFR is greater than the typical delay times for waves propagating between the two spacecraft, this receiver is only included on ISEE-1. For a detailed description of the Plasma Wave Instrument, the reader is referred to the IEEE Geoscience Electronics reference above. A common acronym for the plasma waves instrument in older documentation is GUM, which stands for for Gurnett Mother. Since this acronym is not easily recognizable by the space physics community and since no official acronym is provided in the instrument paper, the more common short hand 'PWI' is used to refer to the Plasma Wave Instrument in this archive.

Time offsets from the Epoch time for each spectral measurement in a sweep. If sub-sweep timing is not important to your application, this value can be ignored. Otherwise for each measurement add this time to the Epoch value for the record. There is one offset in this array for each measurement in the SFR sweep.

Channel Frequency Centers, 128 (104 Hz to 399,000 Hz). These are the frequency channels for all 4 of the SFR bands. The SFR outputs 4 simultaneous measurements, one for each band. In this file those measurements have been reordered by increasing frequency. If needed, the sub-sweep time of each point may be determined using the SubSweepTime variable.

Spacecraft Event Time in UTC for the start of an SFR sweep. To get time offsets within a sweep add the corresponding values in the SubSweepTime array.

These data are collected primarily via the fine wire electric dipole antenna which had a tip to tip length of 215 meters. A small fraction of the data, less that 0.5%, in this variable were collected via the Eu and Es antennas. See the 'Eu_Sensor' variable to distinguish the input sources if needed. The Eu and Ev antennas ware shared with the Heppner DC electric-field experiment. Consult the 'Quality_Flag' variable for issues regarding E_Spectra values.

The ISEE-1 PWI SFR may be connected to one of 4 different input sources, the Eu, Ev, and Es antennas, as well as the Bz search coil. Since the Es antenna was used to provide less that 0.01% of the electric wave measurements and since Es data exhibit a very low sensitivity range, these have been dropped from the CDF archive. This leaves only Eu, or Ev data in the E_spectra variable. The Ev antenna was connected to the SFR 98.3% of the time, while the Eu antenna was utilized less than 0.5% of the time. If the Eu antenna contributed any of the measurements for a sweep then the 'Eu_Sensor' flag is set to 1. If not this flag reads 0.

Integer combining all E-antenna data quality flags, 0 = no issues detected. A bitwise OR'ing of all known issue values for this record. The following issue values are defined. (0x4: MOZER) if this flag is present then the Quasi-static Electric Fields instrument (F. S. Mozer) is performing a bias sweep, (0x8: HARVEY) identifies possible interference that occurs when the Plasma Density instrument (C. C. Harvey) injects signals on either of the long electric dipole antennas.

When set to 1 PWI is in 4x sample rate mode. ISEE-1 Could operate in two telemetry modes, called 'low bit rate' and 'high bit rate'. Low bit rate was more common. During low-bit rate the SFR outputs were sampled once per second. In high bit rate mode sampling was performed 4 times per second. In either case the SFR center frequencies were only changed 1/second. This means that an entire sweep always requires 32 seconds to perform. To keep records consistent across both telemetry modes, in this data set 4 samples taken at a single frequency over the same second are averaged together during high rate telemetry operations. When this flag = 1 each data point is a 4-sample average, when set to 0 each data point represents a single A/D conversion on-board ISEE-1.