image courtesy of Donald Hunton-Air Force Resarch Laboratory
Welcome to the CINDI (Coupled Ion-Neutral Dynamics Investigation) data distribution website at the Center for Space Sciences at the University of Texas at Dallas. We provide the data here from the Ion Velocity Meter (IVM) and the Neutral Wind Meter (NWM) on the C/NOFS satellite. We hope these data will be of use to you and we know you want to get to the database quickly, but please take a few minutes to read over our background material first. Trust us, this will save you a lot of pain and grief later on. For any other questions or requests, please contact Dr. Marc Hairston.
Update July 2011: While there have been some upgrades over the past two and a half years, this is the biggest update we have done and we now consider the data we are presenting here to be of Level-1 quality. Please note these three major changes made to the publicly available data on this website:
1) Correcting the offset. Determining the ion flows from CINDI requires that we know the orientation of the spacecraft (and thus the instruments) to a high degree of accuracy. Unfortunately there have been issues with the orientation data and so there is an inherent uncertainty in the resulting velocity data. Under normal conditions (near solar maximum) where we had complete set of flow data for an entire orbit, it would be straightforward to correct for any offset by averaging the flow over the several orbits. However, since the low plasma densities from extreme solar minimum conditions results in a missing segment of velocity data around the apogee of every orbit, this simple solution was not achievable. Instead we have developed a procedure where we detrend the velocity data over a period of several months and use that to determine the changing offsets in velocity data. The data now being delivered by this website has had the offsets calculated and removed from the ion velocity data. NOTE: because this correction requires data both before and after the given data point, the most recent data (roughly the past month or two) will NOT have the offsets corrected. Obviously we will be updating these data periodically. Please be aware of this if you are using very recent data. There is a "offset flag" in the ascii data file which denotes whether a given data set has been corrected or not.
2) Photoemission contamination. During part of the spacecraft's orbit soon after sunrise there is a short period (roughly a few minutes) where the instrument orientation allows sunlight to shine into the aperture of the IVM in such a way that some photoemission electrons are created behind the repeller grids. These photoelectrons are collected by the instruments and contaminate the reading for the crosstrack ion velocities, thus producing erroneously large velocities. Fortunately the amount of this contamination is predictable and repeatable, so we were able to model it, then use this model to correct the ion velocities. The velocity data now on this website has had the velocity data corrected for the times when this photoemission contamination occurred. Note that the photoemission correction is performed even when the offset correction described above is not.
3) Ion velocities in magnetic coordinates. The ion velocities measured by CINDI are taken in the frame of reference of the spacecraft (x-y-z, or ram direction, horizontal crosstrack direction, and vertical). However, for most scientific work we want the ion velocities given in the coordinate system of the local magnetic field (parallel, perpendicular, and meridional). We now present the ion velocities in both coordinate systems in both the plots and the ascii data on this website. Please note that we only present the data in magnetic coordinates if all three ion velocities in the spacecraft coordinates are available and good. If one or more of these velocities are missing or bad, then no velocities in magnetic coordinates are produced. Also note that the transformation into magnetic coordinates is based on the IGRF model of the terrestrial magnetic field's orientation at the spacecraft's location at that point in time.
Update October 2008: The CINDI project was launched in April 2008 after spending some 4 years in storage. The requirements for on-orbit spacecraft performance and verification coupled with various interruptions due to initial anomalous behaviors resulted in very little CINDI data being taken prior to August 1, 2008. (Specific requests for data prior to August 1, 2008 should be directed to the CINDI team.) Various spacecraft and instrument operations anomalies continue which result in data outages at various times after August 1, 2008.
To date the solar activity levels are among the lowest observed since 1954. F10.7 cm fluxes below 70 W/m2 result in the very cold atmosphere that largely resides below the satellite perigee of 400 km. The Neutral Wind Meter is thus operating at the lowest edge of its sensitivity limit and no reliable wind measurements are yet available. We expect this situation to improve as solar activity levels increase in 2009.
Low solar activity levels also result in the ionosphere being dominated by H+ at altitude above 500 km. Under these conditions the requirement for the spacecraft to be moving supersonically with respect to the plasma is violated and the drift meter performance measuring the crosstrack ion flows (Vy and Vz) is compromised. Again, we expect this situation to improve as solar activity levels increase in 2009. Good data on ion composition, temperature, density, and ram ion velocity (Vx) from the RPA are available above 500 km.
CINDI DATA CAUTIONS and ADVICE
accessible from this web site has undergone a first-order screening to remove
obviously erroneous entries but has not been systematically examined by the
CINDI team to verify the effectiveness of the screening process. A short consult
with the CINDI team prior to extensive analysis of this data would be prudent.
2 . The data may contain small dc biases that cannot be removed prior to the collection of a long-term (several months) data collection period.
3 . Do not proceed with science findings derived from this data without consulting a member of the CINDI team to verify that you are using it appropriately.
CINDI DATA USE RULES of the ROAD
accessed from this web site may not be redistributed to others.
findings resulting from the data extracted from this web site must be communicated
to the CINDI Principal Investigator (R.
A. Heelis) prior to submission for publication or presentation. Please be
aware that the CINDI and C/NOFS programs support a number of graduate student
studies using these data and we do not want to undermine their work. Communication
and collaboration is the key.
3. If the
CINDI investigator team does not participate in a science investigation utilizing
the data from this web site any resulting publication should contain an acknowledgement
to the CINDI investigator team that reads
“CINDI data are provided through the auspices of the CINDI team at the University of Texas at Dallas supported by NASA grant NAS5-01068”
Current state of the available CINDI data
At present there are no data from the Neutral Wind Meter available here for the reasons described above. We hope to begin distributing NWM data sometime in 2009.
Update 14 September 2010 Starting with the 29 July 2010 data we have changed the RPA analysis procedure to improve the accuracy of the data products given the continuing relatively low density of the ionosphere during the end of solar minimum. Note that the analysis now takes into account two complete sweeps of the RPA for a single analysis, so the resolution has dropped to 1 Hz. For the time being the analysis algorithm is still under development so 1) these data (Vx, ion temperature, density and composition) STARTING 29 July 2010 are to be considered VERY PROVISIONAL until further notice and 2) we reserve the right to reprocess and change these data at any time. Please contact us before using these data in any paper or presentation. There have been no change to the data prior to 29 July 2010.
Update 9 December 2009 We have revised our analysis program to correct for the uncertainties in the baselines of the velocity data, primarily the Vy and Vz. A complete correction would require that we have velocity data over an entire orbit and that will have to wait until we come out of solar minimum. In the meantime, this correction is based on our best analysis using the incomplete data we have now. While the velocity data should still be considered provisional until we come out of solar minimum, we are more confident in these values and feel we are relatively close to the true values of Vy and Vz. If you have downloaded data before today (9 December 2009) and are using the velocity data, you will need to download the data again to get the improved data. No other data in the dataset have been affected, so if you are not using the velocity data then you do not need to download the data again.
Update May 2009 We have now placed on-line both the plots and the numerical data (ascii files) from CINDI covering the period from 1 August 2008 through the 31 March 2009. Our current plan is to add a new month's data on-line with about a six week delay, though this is subject to change. Data from instrument turn-on (late May 2008) through 31 July 2008 are available by special request with the understanding that some of those data were taken for calibration and may not be usable for research purposes. Please note that these on-line data are STILL PROVISIONAL. Until ionospheric conditions improve enough that we can make reliable cross-track data for an entire orbit, we cannot establish a reliable baseline for the cross-track data. At present we believe the relative variations in the Vy and Vz data over short periods of time (less than one orbit) are reliable, but we cannot be certain of their absolute values. In addition we are still refining our routine that produces the parameters from the RPA (Vx, ion temperature, ion density, and plasma composition). We are confident in the quality of most of these parameters most of the time, but we can guarantee we will be reprocessing these data several more times before we are fully satisfied with all the data. Last, we are still developing a system of quality flags for these data and hope to have that in place by the end of summer. As always, please contact us before using any of these data in a presentation or publication.
We are working very hard to produce quality data that will be of use to the space science community, and we appreciate your patience.
Back to the CINDI homepage
This data distribution website is supported by NASA through funding for the CINDI Small Explorer program, NASA grant NAS5-01068.