Notes on Space Physics Data Provided through CDAWeb

For all Space Physics data in CDAWeb we provide access to extra notes in the data files themselves at Master Notes.

For ISTP we provide access to ISTP Principal Investigator provided explanatory materials related to the Key Parameter (and in some cases, Higher Resolution) data. Access is through the SPOF maintained Related WWW Sites page for links to the existing sites.

For ISTP we also provide limited notes on identified problems and issues. Click here for Notes on ISTP Key Parameters.

For other Space Physics Data we provide links to Web pages maintained by the Investigator Teams. Click here for Other Space Physics Web sites.

See also NSSDC Space Physics Flight Projects for other background information on the sources - spacecraft or ground-based investigations.



Notes on ISTP Key Parameters

The ISTP Key Parameters are preliminary data intended for use as BROWSE data. Users interested in publication-quality versions of these data are encouraged to contact the appropriate Principal Investigator(s).

The information below is compiled from files kept centrally at the ISTP CDHF until late 1994 and additional important warnings/information as we receive them.


ACE Magnetic Field Detector KP Data Caveat

The Magnetic Field Experiment (MAG) consists of twin vector fluxgate magnetometers controlled by a common CPU. The sensors are mounted on booms extending 4.19 meters from the center of the spacecraft at opposite sides along the +/-Y axes of the spacecraft. The instrument returns 6 vector measurements each second, divided between the two sensors, with onboard snapshot and FFT buffers to enhance the high-frequency resolution.

Browse data for the MAG instrument consists of 16-second, major-frame averages of the measured magnetic field with subsequent analysis yielding 5-minute, 1-hour and 1-day averages consistent with Browse data from other ACE instruments. Instrument offsets, including spacecraft fields, are derived from past weeks of data and necessarily lag behind the most accurate values computed for use in Level-2 analyses. Users of Browse data should be aware that spurious AC signals, such as possible spacecraft or instrument noise, are not detected and are not removed from the Browse analysis. Depending on the accuracy and stability of offsets applied in the above manner, spacecraft spin tones may be evident in the data. MAG data is not guaranteed during spacecraft maneuvers and spacecraft nutation is likely to contribute directional errors following maneuvers.

MAG Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

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ACE Electron, Proton, and Alpha Monitor KP Data Caveat

Note: The Electron, Proton, and Alpha Monitor (EPAM) is designed to make measurements of ions and electrons over a broad range of energy and intensity. Through five separate solid-state detector telescopes oriented so as to provide nearly full coverage of the unit-sphere, EPAM can uniquely distinguish ions (E > 47 keV) and electrons (E > 38 keV) providing the context for the measurements of the high sensitivity instruments on ACE.

The browse parameters contain spin averaged data coming from two of the five telescopes. The full resolution and angular data is available from the Johns Hopkins University Applied Physics Laboratory. EPAM is also part of the real-time Solar Wind (RTSW) system developed by NASA and NOAA. The instrument provides 24 hour coverage of the space weather environment as measured by ACE. For additional information contact Dennis Haggerty (Dennis.Haggerty@jhuapl.edu) or Rob Gold (Robert.Gold@jhuapl.edu).


This 761-1220 keV ion channel is on a telescope referred to as LEFS60 (Low Energy Foil Spectrometer). An aluminized Parylene foil is used to absorb ions with energies below 350 keV while allowing ions above 350 keV to pass through to the solid-state detector. The telescope is mounted at 60 degrees to the spacecraft spin axis. The geometrical factor for this channel is 0.397 (cm2.sr).

These channels come from EPAM's Low-Energy Magnetic Spectrometer which is oriented at 30 degrees from the spacecraft spin axis and is known as the LEMS30 telescope. The LEMS30 telescope contains a rare-earth magnet in front of the detector and sweeps out electrons with energy below about 500 keV. The flux conversions for these browse channels use a geometrical factor of 0.428 (cm2 sr).

These deflected electron channels are a byproduct of EPAM's Low-Energy Magnetic Spectrometer which is oriented at 30 degrees from the spacecraft spin axis and is known as LEMS30. The rare-earth magnet in front of the LEMS30 detector deflects electrons away from the ion detector and samples them in a separate detector known as the B detector. Only deflected electrons can reach the B detector so it is not susceptible to ion contamination The geometrical factor for these channels is 0.14 (cm2 sr).


EPAM Home Page.

EPAM Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

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ACE Solar Isotope Spectrometer KP Data Caveat

SIS Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

Note: During periods of high solar activity, the livetime for these browse parameters may not be calculated correctly, resulting in incorrect flux values.
Two noisy matrix strip in the instrument were turned off on 2000-318. These strips were causing the livetime for these browse parameters to be calculated incorrectly. This is the cause of the apparent large drop in flux on 2000-318.

Integral flux of high-energy solar protons from the T4 and T67 counting rates of the Solar Isotope Spectrometer (SIS). These browse parameters are designed to emulate the SIS proton rates contained in ACE Real Time Solar Wind Data from NOAA.

During solar quiet times, these fluxes are contaminated by background from particles entering from the sides of the instrument.

This browse parameter is derived from the counting rate of energetic CNO nuclei that stop in the two solid state detector telescopes that make up the Solar Isotope Spectrometer (SIS). Included are events with nuclear charge 3 <= Z <= 9 that trigger detectors M1 and M2, and then stop before triggering detector D1. The 3 <= Z <= 9 element range is always dominated by C, N, and O nuclei, independent of the source of the particles being observed.

During solar minimum (e.g., 1992 to 1998), on days when the Sun is quiet, the 7 to 10 MeV/nuc energy interval is dominated by anomalous cosmic ray (ACR) nitrogen and oxygen, with a small contribution (< 10%) from galactic cosmic rays (GCRs). Anomalous cosmic rays originate from interstellar neutral particles that are swept into the heliosphere, ionized, picked up by the solar wind and carried to the solar wind termination shock, where they are accelerated to energies of ~1 to ~50 MeV/nuc. The flux of these nuclei sometimes varies by as much as a factor of ~2 over the 27 day solar rotation period in response to interplanetary conditions. The ~40 cm2sr geometry factor of SIS allows these variations to be seen clearly. As we move toward solar maximum conditions in 1999 and beyond, the flux of ACRs is expected to decrease by a factor of ~100 or more, as it becomes more difficult for low energy cosmic rays to enter the inner heliosphere.

During large solar energetic particle (SEP) events, the intensity of low energy nuclei in interplanetary space can increase by factor of 10 to 1000 or more, and for days at a time, this energy interval can be dominated by solar energetic particles with C:N:O ~ 0.4:0.15:1. An example of such an event is seen in early November of 1997 (~Day 310). The quiet time intensity measured by this browse parameter should vary from ~10-8 per cm2sr.sec.MeV/nuc at solar maximum to ~10-6 per cm2sr.sec.MeV/nuc at solar minimum. During large solar particles events it could be as high as ~1 per cm2sr.sec.MeV/nuc.

Qualifying Remarks:

Note that the energy intervals for the most abundant elements C, N, and O all differ somewhat from the nominal values of 7 to 10 MeV/nuc.

This browse parameter is derived from the counting rate of energetic CNO nuclei that stop in the two solid state detector telescopes that make up the Solar Isotope Spectrometer (SIS). Included are events with nuclear charge 3 <= Z <= 9 that trigger detectors M1 and M2 then stop in either D1 or D2. This element range 3 <= Z <= 9 is always dominated by C, N, and O nuclei, independent of the source of the particles being observed.

This browse parameter responds mainly to anomalous cosmic rays during solar-minimum quiet times, to galactic cosmic rays during solar maximum quiet times, and to solar particles during large solar energetic particle events (see discussion for the 7 to 10 MeV/nuc CNO browse parameter). The quiet time flux should vary from a few x 10-8 per cm2sr.sec.MeV/nuc at solar maximum to ~10-5 per cm2sr.sec.MeV/nuc at solar minimum. During large solar particles events it could be as high as ~0.1 per cm2sr.sec.MeV/nuc.

Qualifying Remarks:

Note that the energy intervals for the dominant elements C, N, and O all differ somewhat from the nominal values of 10 to 15 MeV/nuc, and that the relative abundance of the contributing elements depend on the source of the particles, as noted above and in the description of other SIS browse parameters.

SIS measurements of the intensity of ~9 to ~21 MeV/nuc Z>=10 nuclei are derived from the counting rate of energetic nuclei that stop in the two solid state detector telescopes that make up the Solar Isotope Spectrometer (SIS). Included are events with nuclear charge 10<=Z<=28 (Ne to Ni) that trigger detectors M1 and M2 and then stop in either M2, D1, or D2. The most abundant elements in the element range 10<=Z<=28 are Ne (Z=10), Mg (Z=12), Si (Z=14) and Fe (Z=26).

During solar quiet times this browse parameter responds mainly to galactic cosmic rays, with an admixture of anomalous cosmic ray Ne (see also discussion of 7 to 10 MeV/nuc CNO browse parameter from SIS). During large solar particle events the intensity can be orders of magnitude greater for periods of days. The quiet time intensity should vary from ~10-8 per cm2sr.sec.MeV/nuc at solar maximum to a few times 10-7 per cm2sr.sec.MeV/nuc at solar minimum. During large solar particle events the intensity could rise to >10-2 per cm2sr.sec.MeV/nuc.

Qualifying Remarks:

Note that the quoted energy interval of ~9 to 21 MeV/nuc is strictly valid only for Si. For Ne the corresponding interval is ~8 to ~17 MeV/nuc, while for Fe it is ~12 to ~26 MeV/nuc.

For more information on SIS, see The CRIS/SIS Home Page.

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SWEPAM KP Data Caveat

SWEPAM Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

Proton density (np) -
is the proton number density in units of cm-3, as calculated by integrating the ion distribution function.

Proton speed (vp) -
is the solar wind proton speed, or more generally just the solar wind (bulk) speed. It is also obtained by integrating the ion (proton) distribution function.

Helium ratio (nHe/np) -
is the ratio of the number density of helium++ ions to the number density of protons.

The radial component of the proton temperature (Tp,rr) -
is the (1,1) component of the temperature tensor, along the radial direction. Again, it is obtained by integration of the ion (proton) distribution function.

For more information contact Dave McComas (dmccomas@Lanl.Gov) or visit the SWEPAM website at http://nis-www.lanl.gov/nis- projects/swepam/.

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GEOTAIL Electric Field Detector KP Data Caveat

The sensor providing data here (called EFD-P in Geotail Prelaunch Report, April 1992) measures the difference of electric potential between two electrodes (probes) immersed in the plasma. There are two sperical probes and two wire antennas each of which is extended by 50 meters from the satellite in its rotational plane. The two sperical probes are opposite each other (100 meters tip-to-tip) as are the two wire antennas. The probe pairs are orthogonal to each other. Diving the potential difference by the distance between the probes or the centers of the conducting portion of the wire antennas gives the electric field component along the probe extension. The measurement of the electric field in the satellite rotational plane gives the vector electric field when the electric field along the magnetic field is much smaller than the perpendicular component.

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GEOTAIL Energetic Particles / Ion Composition KP Data Caveat

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GEOTAIL Hot Plasma Analyzer Data Caveat

HPA 1-min data are provisional until calibrations are corrected for long-term drift. Also, caution is advised for occasional telemetry errors.

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WIND Radio/Plasma Waves KP Data Caveat

The Ne variable contains a measure of the plasma density computed by neural networks. This value should always be considered WITH the E_AVERAGE information since it should track the plasma line visible on the dynamic spectrum. Sometimes, however, the neural network value will be unreliable and this is especially true when in proximity to the earth. Visual confirmation will indicate the presence of outliers, or regions where the network is fallible. The parameter Ne_quality may give some estimate of the reliability of the plasma density - but should be used in conjunction with visual inspection.

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Polar TIMMAS KP Data Caveat

The instrumental energy range is subject to change a few times per orbit. Energy_Range_ID indicates which of the 3 instrumental energy ranges is currently active. Each instrumental energy range is further divided into 3 Key Parameter (KP) energy channels (low - medium - and high). The table below gives the full energy range and limits of the three KP energy ranges.

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Polar UVI KP Data Caveat

Plotting problems may occur when too large a time span is selected for IDL to handle (runs out of memory). Please try asking for no more than a few hours of data at a time.

Sampling schemes are in development to accomodate longer time spans.

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Interball MAG KP Data Caveat

For some days the By and Bz components are missing because attitude data is absent and rotating components (i.e. YZ GSE/GSM) can not be restored. Hopefully attitude data will be available in the future. (5/8/96)

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Interball Corall KP Data Caveat

For some days the Vy and Vz components are missing because attitude data is absent and rotating components (i.e. YZ GSE/GSM) can not be restored. Presently, the YZ components are in spacecraft coordinates when the attitude data is missing. This should be changed to fill value (i.e., they will not be plotted) in the next few weeks. (6/16/97)

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IMP-8 MAG KP Data Caveat

Key Parameters for the Magnetometer investigation are computed within the ISTP/CDHF for a week of data at a time. Generally Key Parameter availability lags real time by about 14 days.

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IMP-8 PLA KP Data Caveat

Parameters derived on a routine basis are proton velocity, number density, and temperature (most probable thermal speed). Those parameters are obtained from a non-linear, least-squares fit to the observed fluxes using a convected, isotropic Maxwellian model.

Key Parameters for the Plasma instrument are computed at MIT using Level Zero data that are staged to the ISTP/CDHF approximately two weeks after being received on Earth. Thus the plasma instrument's Key Parameters lag real time by something greater than 2 weeks, but less than four.

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LANL/Magnetospheric Plasma KP Data Caveat

This file contains numerical moments computed from measurements of the Los Alamos Magnetospheric Plasma Analyzer (MPA) [Bame et al., Rev. Sci. Inst., in press 1993]. The moments are presented in s/c coordinates: the z-axis is aligned with the spin axis, which points radially toward the center of the Earth; the x-axis is in the plane containing the spacecraft spin axis and the spin axis of the Earth, with +X generally northward; and the y-axis points generally eastward. Polar angles are measured relative to the spin axis (+Z), and azimuthal angles are measured around the z-axis, with zero along the +X direction. The moments are computed for three 'species': lop (low-ener. ions, ~1eV/e-~130eV/e); hip (hi-ener. ions, ~130eV/e-~45keV/e); alle (electrons, ~30eV - ~45keV ).

The electron measurements are obtained 21.5 secs after the ion measurements. Epoch is the measurement time appropriate for the ions. The moments are computed after the fluxes are corrected for background and s/c potential. Algorithms for these corrections are relatively unsophisticated, so the moments are suspect during times of high background and/or high spacecraft potential. Because the determined spacecraft potential is not very precise, the magnitude of the low- energy ion flow velocity is probably not accurate, but the flow direction is well determined.

Tperp and Tpara are obtained from diagonalization of the 3-dimensional temperature matrix, with the parallel direction assigned to the eigenvalue which is most different from the other two. The corresponding eigenvector is the symmetry axis of the distribution and should be equivalent to the magnetic field direction. The eigenvalue ratio Tperp/Tmid, which is provided for each species, is a measure of the symmetry of the distribution and should be ~1.0 for a good determination.

Several of the parameters have a fairly high daily dynamic range and for survey purposes are best displayed logarithmically. These parameters are indicated by non-zero 'SCALEMIN' values in this file. A quality flag value of 1 indicates that the values are preliminary and have not been checked in detail.

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LANL/Synchronous Orbit Particle Analyzer KP Data Caveat

Electron, proton and helium measurements are taken every 160 ms from one of the three telescopes according to the following sequence: T1, T2, T3, T2, T1, T2 etc. Heavy ion data accumulated from each of the three telescopes again according to the timing and sequence above and summed for 10.24 seconds which is approximately one spacecraft rotation. SOPA Key Parameters are normally averaged over three telescopes for ~ 1 minute (6 - 10.24 second data accumulation cycles) giving an average over much of the sky. The time associated with each set of Key Parameters is determined by using the time (in minutes of the day) at the start of each data collection cycle as an index into an array of 1440 time slots dividing the day into 1440 one minute intervals. The time reported is the midpoint of each interval.

We provide six fluxes: Low energy Protons: 50 keV to 400 keV High energy Protons: 1.2 MeV to 5 MeV Low energy Electrons: 50 keV to 225 keV High energy Electrons: 315 keV to 1.5 MeV Helium : ~0.9 MeV to ~1.3 Mev Heavy Ions : ~5 MeV to ~15 MeV (includes carbon, nitrogen, and oxygen We also compute two electron temperatures and densities and two proton temperatures and densities. These are based on approximately the same energy ranges as the fluxes given in above and are determined for relativistic Maxwellian distributions.

Status of SOPA Instrument 1989-046: Operating normally as of 01-Feb-1993

Status of SOPA Instrument 1990-095: Loss of all ion data as of July 1992 All three thin, front, D1 detectors have failed, having become intolerably noisy. The net result of this failure is the complete loss of proton, helium, carbon, nitrogen, oxygen and other high Z Key Parameter data from the instrument. Since all three thick, back D2 detectors are still operating normally, the electron measurements remain only insignificantly affected.

Status of SOPA Instrument 1991-080: Operating normally as of 01-Feb-1993 with the following exception. Detector D1 on Telescope 2 is becoming noisy. This affects proton and ion data from that telescope. Bad data is disabled thru software in the ground processing and is NOT averaged into the Key parameter data. Therefore, the parameters given are good but do not cover the same percentage of the sky.

Data is flagged with a data quality flag as follows: +1 Data is Good 0 Data is Suspect -1 Data is Unusable LANL personnel should be contacted before using any data tagged as suspect.

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GOES 6 and 7 KP Data Caveat

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GOES 6 - Magnetometer KP Data Caveat

(the following quality information was provided by Dr. Howard J. Singer, Acting Chief Geospace Branch, NOAA R/E/SE 303- 497-6959) :

A variety of malfunctions of the spin plane components (He and Hn) of this instrument have occurred since at least September 1992. These data are useful for detecting a variety of disturbances in the space environment, but the actual field values are not to be trusted. The parallel, or spin axis, component (Hp) of the field appears to be unaffected by the spacecraft or instrument difficulties; however, the offset of this component is difficult to calibrate and questionable. Interpretation of the data is also complicated by the fact that the GOES 6 spacecraft orbit has become more inclined to the equatorial plane than is typical of the GOES satellites.

GOES 7 - Magnetometer KP Data Caveat

(the following quality information was provided by Dr. Howard J. Singer, Acting Chief Geospace Branch, NOAA R/E/SE 303- 497-6959) :

The GOES 7 magnetometer transverse components (He and Hn) failed on May 2, 1993. At this time an offset also appeared in the spin axis component. This offset was removed on May 18, 1993; however as with GOES 6, the absolute value of the spin axis component also has uncertainties.

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Energetic Particle Detectors KP Data Caveat

(the following quality information was provided by Dr. Herb Sauer NOAA R/E/SE 303-497-3681) :

The GOES E1 and P1 channels were designed to measure the geostationary flux of electrons of energy E > 2 MeV and protons of energy E such that .6 > E > 4.2 MeV. Because of radiation damage to the GOES-6 E1 detector, these data are not included in the data-set. The GOES -7 electron detector also responds to protons of energy E > 80 MeV. Therefore, during solar energetic particle events, the electron data are often compromised to the extent that they may primarily represent the detector response to energetic protons. GOES-7 particle detector data is missing during an eclipse and for approximately the following 4 hours.

Finally, the geomagnetic cutoff at geostationary orbit is of the order of 1 MeV, which is within the energy range of the P1 channel. Therefore, the flux observed during a solar energetic particle event by channel P1 is a composite of trapped protons at the lower channel energies and event protons which reach the satellite from sources outside the magnetosphere.

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Author and Curator


Authorized by R.E. McGuire, Head, Space Physics Data Facility
(Code 672, NASA/GSFC), Robert.E.McGuire@nasa.gov, (301)286-7794


Last Modified:Monday, 23-Jun-2009