ISTP NEWSLETTER Vol 6, No. 2. June, 1996
http://pwg.gsfc.nasa.gov/istp/newsletter.html
This map shows the count rate of electrons with E>1 MeV measured by SAMPEX as a function of
geographic longitude and latitude. See "An Assessment of Space Environmental Conditions During
the Recent Anik E1 Spacecraft Operational Failure", pg 8
Title Author
The Value of Science Nuggets and Gems - Jim Willett
Data Products Available to the General Scientific Community - Jim Willett
New Access (CDAWeb) to ISTP's Key Parameter Data - R. L. Kessel, R. J. Burley, R. E. McGuire, M. Peredo
An Assessment of Space Environmental Conditions During the Recent Anik E1 Spacecraft Operational Failure - D.N. Baker, J.H. Allen, R.D. Belian, J.B. Blake, S.G. Kanekal, B. Klecker, R.P. Lepping, X. Li, R.A. Mewaldt, K. Ogilvie, T. Onsager, G.D. Reeves, G. Rostoker, R.B. Sheldon, H.J. Singer, H.E. Spence, N. Turner
Statistical Analysis of the Receipt of WIND and POLAR Command Files - Chris Raymond, Bruce Samuelson
New ISTP products on the SPOF World Wide Web Server - Mauricio Peredo, Scott Boardsen, Daniel Berdichevsky, Greg Galiardi
Editor:
Michael Cassidy
CASSIDY@ISTP1.GSFC.NASA.GOV
Contributing Editors:
Steven Curtis - Science Editor
U5SAC@LEPVAX.GSFC.NASA.GOV
Doug Newlon - Data Distribution Facility
NEWLON@IPDGW1.NASCOM.NASA.GOV
Kevin Mangum - Central Data Handling Facility
MANGUM@ISTP1.GSFC.NASA.GOV
Dr. Mauricio Peredo - Science Planning and Operations Facility
PEREDO@ISTP1.GSFC.NASA.GOV
Dick Schneider - ISTP Project Office
SCHNEIDER@ISTP1.GSFC.NASA.GOV
Jim Willett - NASA Headquarters
WILLETT@USRA.EDU
J. B. Willett
ISTP Project Scientists have been asked to contribute science nuggets to NASA Headquarters at approximately monthly intervals. These nuggets are typically a paragraph or two, and give a very brief description of current science activities for each mission (WIND, POLAR, SOHO, GEOTAIL, and the Ground-Based element of ISTP). The information keeps the Program Manager, Program Scientist, and Science Program Director at Headquarters aware of the scientific productivity of the programs for which they are responsible. This can be beneficial to ISTP and can help strengthen the case for maintaining a strong ISTP program in the future.
Science gems are also one to two paragraph notes to NASA Headquarters which describe particularly
interesting results, discoveries, events, etc. and which are to be contributed as they occur. The gems
may be generated by any ISTP investigator, but should be submitted with the concurrence of the
appropriate PIs and Project Scientists. These are generally very preliminary and well prior to public
announcement. Gems are one good indicator of the potential value for an investigation or mission.
Dr. James B. Willett
Manager, Mission Operations & Data Analysis, for Space Physics
NASA Headquarters
Code SR
300 E Street SW
Washington DC 20456
(202) 358-0888
james.b.willett@hq.nasa.gov
willett@usra.edu
J. B. Willett
Recently PIs and Project Scientists took part in an effort to generate information on the data products from ISTP that are currently available or will be made available to the general scientific community. This information was forwarded to the Mission Operations and Data Analysis Manager for Space Physics Missions at NASA Headquarters. The variety of formats and level of content covered an extremely wide range. This information has been forwarded to the Space Physics Data Facility (SPDF) at GSFC to be distilled into 1 to 2 page formatted summaries. Bob McGuire, head of the SPDF, is in charge of this effort.
These one to two page summaries will be used to augment NASA Research Announcements (NRAs) in which mission data will be used, such as in the ISTP Guest Investigator Program that has just been announced. The summaries will also be used to track an investigator's performance regarding data product delivery to the science community, and as such must be a living document. It is intended that these pages will be on the WorldWide Web (WWW).
The summaries will be returned to the project scientists shortly for review and corrections, and almost certainly all data providers will be asked to review the summaries of their own data products. We ask each data provider to help make these summaries accurate and up-to-date.
It is the intent of the NASA Headquarters Program Management to set up a standing review panel to evaluate the data submissions of investigators and projects for use by the science community at large. Submissions may be made to NSSDC, or other suitable data repository/server, including one's own WWW site. Although having data on a web site may constitute availability, a deep archive of that data in a national repository may still be required.
Ultimately, we wish to preserve the long term legacy of each NASA funded investigation so that the
data can still be used by new investigators without the assistance of PIs or their teams. This reduces
the workload on the PI-teams and allows for the possibility of continuing data analysis after the PI
-team members have moved on to other projects. This requires adequate documentation and possibly
software to accompany the actual data products. The standing review panel will also examine these
supporting data products.
Dr. James B. Willett
Manager, Mission Operations & Data Analysis, for Space Physics
NASA Headquarters
Code SR
300 E Street SW
Washington DC 20456
(202) 358-0888
james.b.willett@hq.nasa.gov
willett@usra.edu
R. L. Kessel, R. J. Burley, R. E. McGuire, M. Peredo
The NASA/GSFC Space Physics Data Facility (SPDF) and the National Space Science Data Center (NSSDC) have just released a new, World-Wide-Web-based system for accessing the public ISTP Key Parameter (KP) database : CDAWeb, the Coordinated Data Analysis (Workshop) Web.
ISTP spacecraft Key Parameters supply particle and field measurements at approximately 1 minute resolution. Geotail KPs include low-energy electron and ion fluxes at 32 energies and 4 look directions; plasma density, pressure and bulk flow velocity; energetic particle differential and integral fluxes, abundance ratios, anisotropies; and magnetic and electric field components, spacecraft potential and bias current. Wind KPs include ion and electron density, velocity and temperature, ion (proton, He, CNO, Iron) and electron fluxes, electric field background, transients, and average values at 76 frequency values, and magnetic field components. Additional particle and field KPs are provided by ancilliary spacecraft such as IMP-8 and the LANL and GOES geosynchronous satellites. Ground -based investigations such as HF Radars, VLF/ELF/ULF Radars, Incoherent-Scatter Radars, Magnetometers, Riometers, Sounders, Photometers and an All Sky Imager, provide data at anywhere from 1 minute resolution to 30 minute resolution depending on the type of measurement. In many cases the data are more complicated than can be displayed in simple time series plots, and thus are displayed as e.g., spectrograms, images, or ionospheric convection patterns.
The easiest paths to CDAWeb access to the full set of ISTP Key Parameters are from either the Space Physics Data Facility home page at URL http://nssdc.gsfc.nasa.gov/spdf/ or the NSSDC Space Physics home page at URL http://nssdc.gsfc.nasa.gov/space/space_physics_home.html or the ISTP page at URL http://pwg.gsfc.nasa.gov/
We believe this is a powerful new capability to better leverage the combined KP database to accomplish the coordinated science objectives of ISTP. We invite you to take this opportunity to look for events in the key parameter data sets, possibly events that you have found already through analyzing other data. Resident with the data is the necessary information (metadata) on labels, time tags, dependencies, display types, etc. so that the steps needed to actually display the data are minimal. (note: The ISTP Key Parameters are preliminary data intended for use as BROWSE data. Users interested in publication-quality versions of this data are encouraged to contact the appropriate Principal Investigator(s).)
To use CDAWeb:
The data are then processed and returned (as plots or listings). The plots are in fact a set of GIF image(s) that can be easily downloaded for local save if desired. The listings can be displayed to the screen, saved directly as (an) ASCII file(s) (as an option of your local browser/use "source" mode), or you can download the CDF data files themselves. At this time, the type of plot used for a particular variable is pre-selected and cannot be changed. Other plot types and functionality will be added in future. (We note that the powerful underlying plot software is in IDL and we plan to make this software accessible in the fairly near future.)
We would also like to point out that the SPDF home page has links for access to SPyCAT (NSSDC /SPDF's Space Physics Catalog web interface to the more comprehensive NDADS near-line archive), access to other CDAWeb databases (such as the IACG 1st Campaign, the Geotail-Wind Magnetopause Skimming Campaign and an Education testbed database of select CDAW-9 data), and access to other useful information and tools. One such tool (Gif_walk) aids access to a database of orbit plots created by the ISTP Science Planning & Operations Facility (SPOF) based from the SPDF/NSSDC Satellite Situation Center software and database. Gif_walk is also configured for access to the SPOF's database of existing standard summary plots of Key Parameters being used to check Key Parameter data quality and to identify events.
Please note the platforms supporting these large databases are being upgraded now, but response may be somewhat slow until these upgrades are complete. This full ISTP KP data access will be the largest -scale user exposure to the system to date, and the first wide exposure of the system combined with this database. Please report any anomalies or problems as they are seen in your testing and use.
We hope you like what we've done. For questions or comments on CDAWeb, please contact either Mona Kessel (301-286-6595, kessel@ncf.gsfc.nasa.gov ) or Bob McGuire (301-286-7794, mcguire@ncf.gsfc.nasa.gov)
R. Burley
BURLEY@NSSDCA.GSFC.NASA.GOV
R. McGuire
MCGUIRE@NCF.GSFC.NASA.GOV
R. Kessell
KESSEL@NSSDCA.GSFC.NASA.GOV
NASA
Goddard Space Flight Center
Code 632.0
Greenbelt, Md. 20771
M. Peredo
Raytheon STX
Goddard Space Flight Center
Greenbelt, Md. 20771
PEREDO@ISTP1.GSFC.NASA.GOV
D.N. Baker, J.H. Allen, R.D. Belian, J.B. Blake, S.G. Kanekal, B. Klecker, R.P. Lepping, X. Li, R.A. Mewaldt, K. Ogilvie, T. Onsager, G.D. Reeves, G. Rostoker, R.B. Sheldon, H.J. Singer, H.E. Spence, N. Turner
Summary
A serious operational failure occurred onboard the Anik E1 spacecraft at geostationary orbit on 26 March 1996 at 2047 UT. The satellite lost half of its solar power panels, thereby causing a reduction by about two-thirds of its communication throughput capacity. In this report we discuss other known operational problems of spacecraft at, or near, geostationary orbit at about the same time as the Anik problem. We also show data from the CANOPUS ground-based array as well as solar, solar wind, and magnetospheric satellites in order to assess environmental conditions that might have played a role in the identified anomalies. We conclude that the high-energy (E>~ 1 MeV) electron flux in the outer magnetosphere was greatly elevated compared to normal, quiescent conditions. The amplitude and the duration (~2 weeks) of relatively high electron fluxes suggests that spacecraft deep-dielectric charging could have played a role in causing, or exacerbating, the Anik E1 problem.
Anik Failure Description
The Telesat Canada Anik E1 communication satellite located at 111 deg W at geostationary orbit suffered a severe operational problem on 26 March 1996. The Anik satellite lost all power from its south solar panel array when it was effectively disconnected from the satellite payload at 2047 UT [1]. The 50% power loss reduced the spacecraft's capacity from 24 C-band channels to nine channels and it reduced the Ku-band capacity from 32 channels to 10 [2]. It is not expected that the lost solar panel can be recovered, thus this was a permanent degradation of communication capability for Telesat Canada. It affects a broad range of video, voice, and data services throughout North America [2]. Service to Telesat Canada customers was restored after about six hours by link switches to other spacecraft and by using backup systems such as fiber optics ground links.
The Anik failure has been determined to be a disconnect of the power distribution unit (PJU) connecting two batteries to the south half of the solar power array. When recovery from orbit of a failed operational spacecraft is impossible, it is usually difficult to infer an exact cause of failure. Evidence is typically limited to knowledge of the final crucial hardware component that failed, to space environment data collected by other satellites and ground-based systems, and to the listing of anomaly histories of other spacecraft around the critical time. It is not clear at this time where, exactly, within the satellite the recent Anik E1 failure occurred. It could have been in the battery system, in the connecting circuitry, or in the solar panel unit itself [3]. The failure mechanism is unclear: It could be a random part failure or related engineering failure. However, it is also conceivable that the space environment may have played a role in the anomaly. We assess general space weather conditions in this report.
Reported Spacecraft Anomalies in late-March 1996
It is of interest, from a circumstantial point of view, to judge whether other spacecraft operational anomalies occurred around the time of the Anik E1 failure. We have learned of several other anomalies and discuss those briefly here.
A Satellite Anomaly Assessment by the USAF 50th Weather Squadron concluded that "Available data indicate that the space environment had a high probability of causing the power disconnect between the solar panel array and the main payload of the Canadian communications satellite ANIK E1 at 26 /2047Z Mar 96.". [4] This assessment took account of the known significant anomaly on a DSCS military communication satellite at geostationary orbit at 0335 UT on the 26th, of GPS navigation satellite operational problems, and of anomalies on other satellites.
It was also reported that the DRA-delta spacecraft suffered state switches on 19 and 26 March 1996 [5]. These geostationary orbit satellites are European communication spacecraft. The DRA-delta switching events have been shown conclusively to be due to deep dielectric charging caused by high-energy electrons [6,7].
A series of four commercial communication satellites at geostationary orbit reported 10 operational anomalies in March 1996. Of these, 8 occurred in the period 13-28 March and 2 occurred on 27 March (the day following the Anik E1 problem). The problems were in the automatic pointing control (APC) circuitry, and prior to the series of problems in late-March, there had been a general reduction of such anomalies in 1996 compared to the past two years. These APC "glitches" occur more frequently on older series satellites either because design changes have mitigated the environmental susceptibility of newer ones or radiation exposure in orbit increasingly degrades environmental resistance. These APC anomalies are mainly minor events, although some have been associated with lost service. Generally, operational policy by spacecraft controllers is to avoid commands to satellites during times of high anomaly rates to avoid the opportunity of producing a combination of malfunctions [8].
There are reports of problems on two other spacecraft at geostationary orbit on, or about, the 26th of March. Owing to security concerns, details of these events cannot be discussed here. We have also received word that Global Positioning System (GPS) satellites experienced operational problems in late March [4].
Overall, the flurry of operational problems for spacecraft in late-March of 1996 suggests that the space environment may have been relatively hostile. Thus, we have examined available scientific and operational data to assess the magnetospheric conditions surrounding the Anik anomaly period.
Solar-Terrestrial Conditions 1996
Prior studies (e.g., [9, 10] and references therein) demonstrate that high-speed solar wind streams can interact with the Earths magnetosphere to produce high fluxes of relativistic electrons in the outer radiation belts. These very energetic electrons, in turn, can cause significant operational anomalies in spacecraft at, or near, geostationary orbit. It was concluded, in fact, that such high-energy electrons produced deep-dielectric charging in the Anik E1, Anik E2, and Intelsat K satellites during a period of severe operational anomalies in January 1994 [9, 10].
Given these past operational sensitivities to the solar wind and magnetosphere conditions, we have used data from several scientific and operational spacecraft to assess conditions in late-March 1996. The data from the beginning of 1996 are employed to provide a broad context for judging the relative hostility of the space environment on 26 March, i.e., the day of the Anik E1 failure.
Fig. 1 Hourly averages of the solar wind speed measured
by the SWE investigation onboard the WIND spacecraft for
the first 100 days of 1996.
Since high-speed solar wind is thought to be a fundamental driver of radiation belt enhancements, we first show measurements of the solar wind speed as obtained from the Solar Wind Experiment (SWE) onboard the WIND spacecraft. WIND was occasionally in the magnetosphere during perigee maneuvers, but we only show SWE data for times when WIND was in the region upstream of the Earths magnetosphere. Figure 1 shows hourly-average solar wind speed data from Day 1 (1 January) to Day 100 (9 April) 1996. It is evident from the plot that there were several strong solar wind stream events throughout early 1996. Notable examples of solar wind speed peaks include those occurring on Days ~15, ~42, ~57, ~72, and ~82. A data gap occurred in our records around Day 30, but it appears that a speed peak also occurred on ~Day 28. Obviously, there were recurrent streams that were associated with the 27-day solar rotation period: The interleaving of two sets of such recurrent streams produced an ~13-day stream enhancement pattern. The Anik E1 failure (Day 86) occurred following a particularly large and complex solar wind enhancement. (The WIND satellite was inside the magnetosphere on Days 86 and 87).
Fig. 2.(a) A soft x-ray image of the Sun (courtesy of L. Acton and L. Bargatze) taken by the Yohkoh
spacecraft at 0956:36 UT on 9 January 1996. A coronal hole is seen near central meridian extending
from the south polar region across the equatorial plane.
Given the well-known fact that the largest solar wind streams originate from solar coronal holes (e.g., [11]), we have examined available solar soft X-ray (Yohkoh) and extreme ultraviolet (SOHO) data to identify solar wind stream source regions. Figure 2a shows a Yohkoh soft X-ray image of the sun taken at 0956:36 UT on 9 January 1996 (courtesy of L. Acton and L. Bargatze). A large, trans-equatorial coronal hole is evident near central meridian. This hole undoubtedly gave rise to the solar wind stream which the Earth encountered on 14 Jan. (see Figure 1). This same coronal hole was seen to return in early February and again in early March of 1996.
Fig 2.(b) An image of the sun taken by the EIT experiment onboard the SOHO spacecraft at 1333:37
UT on 19 March 1996 (courtesy of J.-P. Delaboudiniere and J. Gurman).
A second source of information about solar drivers of solar wind at 1 AU is the SOHO spacecraft located in orbit around the L1 (Lagrangian) point upstream of the Earth. Figure 2b shows an image from the SOHO EIT telescope (Fe XII line at 195 angstroms) taken at 1333:37 UT on 19 March (courtesy of J.-P. Delaboudiniere and J. Gurman). As is evident from the figure, it is hard at this epoch (Day 79) to pick out the coronal hole for the very quiet sun. Nonetheless, as seen in Figure 1, this region of the sun produced a solar wind stream that the Earth encountered several days later (on ~Day 82 = 22 March).
Fig. 3(a) The top panel shows GOES-8 measurements of electrons with E>2 MeV for January to early
April of 1996. The lower panel shows solar wind speed for the same time period (see Fig. 1).
The Anik E1 failure occurred at geostationary Earth orbit (GEO). It is most relevant therefore, to examine conditions at GEO. In the upper panel of Figure 3a, we show data from GOES-8 for electrons with E>2MeV. The lower panel of Figure 3a again shows solar wind speed from 1 January to early April. Note that the GOES data are shown as 5-min averages and the diurnal modulation due to day -night magnetic trapping effects is evident. However, looking at lower frequency flux patterns we see from Figure 3a that each solar wind stream produced a large and relatively brief enhancement of >2 MeV electron fluxes (e.g., in mid-January, in February, and in early-March). On the other hand, the strong and complex solar wind variations of late March produced a long-lasting (>2 week) enhancement of relativistic electrons at GEO beginning on ~12 March; this persisted until essentially the beginning of April.
Fig 3.(b) Energetic electron data from LANL instruments aboard
S/C 1990-095 at geostationary orbit.
Very much the same electron behavior is seen in the data from Los Alamos National Laboratory (LANL) sensors onboard another series of geostationary spacecraft. The data in Figure 3b are from S/C 1990-095 for several energy channels. The data show that electrons from 0.7 MeV to 6.0 MeV were elevated in association with each solar wind stream in early 1996, but the largest and most persistent flux enhancement was seen from ~Day 72 to ~Day 92 (12 March to 1 April).
Fig. 4 SAMPEX daily-average data at L==5 for 2-6
MeV electrons (bottom panel). The solar wind speed is
also shown for reference (top panel). The time of the
Anik E1 failure is indicated.
It was not only the GEO region that showed elevated electron fluxes. Figure 4 (bottom) shows 2-6 MeV electron intensities measured by SAMPEX at low Earth, polar orbit. A subset of the data averaged each day for L=5 (+/- 0.1) is plotted for the period Day 1 to Day 100 of 1996. The upper panel of Figure 4 again shows the concurrent solar wind speed for reference. The SAMPEX data show the relatively brief flux peaks associated with solar wind streams in January and February, but the larger and longer lasting flux enhancement of late-March is quite clear. The Anik failure occurred after a relatively strong, persistent flux peak.
Fig. 5 Bottom panel: A detail of solar wind speed for
Days 60-100 of 1996. Top panel: Hourly averages of
the interplanetary magnetic field Bz component for
Days 75-86.
Fig. 6 Top panel: Daily Ap magnetic index data for
1996. Bottom panel: Daily fluences of >2 MeV electrons
from GOES 8. 594, Part II, pp. 48-61, February 1994.
A key to enhanced geomagnetic activity and eventual relativistic electron production within the magnetosphere is a combination of high solar wind speed and strongly southward interplanetary magnetic field (IMF). Figure 5 shows in the bottom panel the solar wind speed (VSW) from Day 60 through Day 100. In the upper panel, we show hourly averages of the IMF north-south component (Bz) for Days 75-86. We see that the IMF was rather strongly and persistently southward from Day 77 (17 March) to near the end of Day 81 (21 March). This negative Bz was "piled up" at the leading edge of the high-speed solar wind stream which began on ~Day 80 (20 March). As seen in the upper panel of Figure 6, the southward IMF and high value of VSW produced a notable increase in the global magnetic index, Ap. The Ap value peaked on 19 March when the negative IMF was a maximum, but the GOES-8 electron fluence (bottom panel of Fig. 6) peaked several days later.
Fig. 7 Riometer data taken at stations of the CANOPUS array of ground based detectors operated by the
Canadian Space Agency. The top five traces are from stations arrayed along the 265=A1 east geographic
meridian spanning the average auroral zone, while the bottom two traces are from stations in the average
auroral zone one time zone to the west. The absorption events from ~1900-2000 UT are clear evidence for the
presence of energetic electron fluxes in the noon sector (local noon at ~265=A1 east is ~1815 UT).
Data from the CANOPUS riometer chain showed that the enhanced high-energy electron fluxes produced unusually intense electron precipitation on the dayside of the Earth throughout the time period of Day 73 to ~Day 92. The traces in Figure 7 show large and complex riometer absorption signals at nearly all stations in the CANOPUS chain near local noon (and near the meridian of Anik E1) on Day 83 (23 March). This is indicative of very elevated electron fluxes throughout the outer radiation belt [12].
Fig. 8 L sorted SAMPEX electron data for
Days 60-100 of 1996 showing conditions associated with the Anik failure. The data are
shown for each day at L=4, ==5, and ==6.
A more extensive examination of the SAMPEX data at low-Earth orbit fully supports the idea that relativistic electrons were substantially enhanced for nearly two weeks throughout the outer trapping zone. Figure 8 shows L sorted data for electrons with 2 <~E <~ 6 MeV for the period 1 March to 9 April (Day 60-100). It is seen that at each selected L-value (=4, 5, and 6), the electron fluxes dropped to very low values around Day 70 (~10 March) and then the fluxes increased rapidly thereafter. There was a slight drop on ~Day 81 with a persistent climb in flux values after that time until ~Day 90. The Anik failure occurred near a time of maximal relativistic electron flux levels.
SAMPEX Northern Hemisphere
>1 MeV Electrons
7 March 1996
Fig.9a Global image map of the flux of >1 MeV electrons in the northern hemisphere for day 67, 1996.
SAMPEX Northern Hemisphere
>1 MeV Electrons
9 March 1996
Fig.9b Global image map of the flux of >1 MeV electrons in the northern hemisphere for day 69, 1996.
SAMPEX Northern Hemisphere
>1 MeV Electrons
26 March 1996
Fig. 9c Global image map of the flux of >1 MeV electrons in the northern hemisphere for day 87, 1996.
The global extent of the radiation belts is shown in a sequence of northern hemisphere radiation belt projection maps in Figure 9. These maps show the count rate of electrons with E>1 MeV measured by SAMPEX as a function of geographic longitude and latitude. The rather detailed latitudinal measurements and the coarse (16 orbits/day) longitudinal samples are contoured and laid down on a global grid [13]. Figure 9a shows the radiation belt pattern for 7 March 1996. The bright red collar around the northern polar region shows that the outer radiation belt was rather intense as a result of a small solar wind stream that peaked on ~5 March. [Note that the bright red pattern near the bottom of the image is relatively constant and is due to the South Atlantic Anomaly]. Figure 9b shows that the radiation belts, at least at low altitude, had virtually disappeared by 9 March (see Figure 8). After the minimum flux conditions of 9-10 March, the radiation belts strongly recovered. Figure 9c shows that the outer zone was very strong and wide on 26 March 1996, the day of the Anik failure.
Fig. 10a POLAR spacecraft data for high-energy electrons measured by the CEPPAD/HIST detector. 10 March 1996 data. The spacecraft location in L and local time (LT) is shown in the bottom panel.
Fig. 10b POLAR spacecraft data for high-energy electrons measured by the CEPPAD/HIST detector 26 March 1996 data. The spacecraft location in L and local time (LT) is shown in the bottom panel.
A final view of the electron environment in the outer zone is provided by the CEPPAD investigation onboard the recently launched POLAR spacecraft [14]. The High-Sensitivity Telescope (HIST) sensor on POLAR measures 0.4 to >10 MeV electrons. In Figure 10a, we show data for a portion of 10 March 1996 when the radiation belts were rather weak. We see that HIST Channel 10, for example, reached a peak counting rate of only 10 x3 counts/sec. Later, when the radiation belts were much more intense, the flux of electrons measured by HIST was much greater. For example, Figure 10b shows a comparable pass through the radiation belts to that of Figure 10a for 26 March 1996. On this latter day, the peak HIST/Ch. 10 counting rate was ~10 x4 c/s and the entire outer zone profile was much broader in time. This indicates a very much more substantial outer zone electron population.
Concluding Remarks
We have presented evidence in this report that there were several spacecraft operational anomalies during the same period of time as the Anik E1 failure. This suggests a relatively hostile space environment. Indeed, a remarkable array of scientific and operational spacecraft allow us to show that the high-energy electron environment was quite elevated throughout late-March 1996. The satellite and ground-based data suggest that the space environment could have caused, or at least exacerbated, the conditions onboard Anik E1 that led to the power failure that crippled the spacecraft.
As is the case for most on-orbit anomalies, we do not know, and probably will never be able to determine, whether the space environment was a significant factor in the Anik failure. However, we have shown using data from several scientific experiments that the radiation environment was enhanced and should be considered in the anomaly analysis.
Acknowledgments
The authors of this report thank the numerous people who have unselfishly shared their knowledge and data. We gratefully acknowledge Capt. S. Quigley of the 50th Weather Sqdn. Special thanks are given to L. Bargatze and L. Acton for Yohkoh data and to J. Gurman and J.-P. Delaboudiniere for SOHO data. We also thank members of the SAMPEX, POLAR, WIND, GOES, and various other operational spacecraft teams for unflagging support. Ground-based data from the NOAA-NGDC and from CANOPUS have been especially appreciated.
References
[1] Danylchuk, J., Edmonton Journal, 27 March 1996.
[2] Robert, O.L., Space News, p. 4, 1-7 April 1996.
[3] Private Communication to J.H. Allen, 15 April 1996.
[4] Quigley, Capt. S., Satellite anomaly assessment, 50th Space
Wing, provided to J.H. Allen, 29 March 1996.
[5] Private Communication from G. Wrenn to J.H. Allen, 15 April 1996.
[6] Wrenn, G.L., J. Spacecraft and Rockets, 32, pp. 514-520, 1995.
[7] Wrenn, G.L., and A.J. Simms, Proc. Workshop on Radiation
Belts, Models, and Standards, Brussels, in press, 1996.
[8] Private Communication to J.H. Allen, 15 April 1996.
[9] Baker, D.N., S. Kanekal, J.B. Blake, B. Klecker, and
G.Rostoker, Eos, Trans. AGU., 75, p. 401, 1994.
[10] Allen, J.H., Solar-Geophysical Data: Comprehensive Rep., No.
[11] Feldman, W.C., et al., J. Geophys. Res., 83, 2177, 1978.
[12] Rostoker, G., S. Skone, D.N. Baker, Paper presented at IUGG
Meeting, Boulder, CO, July 1995.
[13] Kanekal, S., and D.N. Baker on SAMPEX Web Site (URL):
http://lepsam.gsfc.nasa.gov/www/public_sampex.html
[14] Blake, J.B., et al., Space Sci. Rev., 71, 531, 1995.
D.N. Baker
LASP/Campus Box 590
University of Colorado
Boulder, Co 80303
J.H. Allen
SCOSTEP Secretariat
NOAA/NGDC
Boulder Co
R.D. Belian
Los Alamos National Laboratory
Los Alamos, NM 87545
J.B. Blake
Aerospace Corp.
Los Angeles, Ca
S.G. Kanekal
Raytheon/STX
NASA/GSFC
Greenbelt, Md 20771
B. Klecker
Max Planck Institut
Garching b.
Munchen, Germany
R.P. Lepping
NASA/GSFC
Greenbelt, Md 20771
X. Li
LASP/Campus Box 590
University of Colorado
Boulder, Co 80303
R.A. Mewaldt
Calif. Inst. of Technology
Pasadena, Ca
K. Ogilvie
NASA/GSFC
Greenbelt, Md 20771
T. Onsager
Space Environment Center
NOAA
Boulder, Co
G.D. Reeves
Los Alamos National Laboratory
Los Alamos, NM 87545
G. Rostoker
University of Alberta
Edmonton,Alb., Canada
R.B. Sheldon
Center for Space Physics
Boston University
Boston, Ma
H.J. Singer
Space Environment Center
NOAA
Boulder, Co
H.E. Spence
Center for Space Physics
Boston University
Boston, Ma
N. Turner
LASP/Campus Box 590
University of Colorado
Boulder, Co 80303
Bruce Samuelson and Chris Raymond
The ISTP Science Planning and Operations Facility (SPOF) is tasked with (among other things) receiving instrument commands, and resolving science conflicts between instruments on the GGS WIND and POLAR spacecraft. The SPOF acts as a relay between the PI teams and the Command Management System (CMS). One of the design goals for the SPOF was to accept command files through the standard UNIX e-mail interface with minimal human interaction. The software became operational with the launch of the WIND spacecraft.
The number of commands flowing through the SPOF system dramatically increased when the POLAR spacecraft was launched. Initially the software was configured to handle the lower volume of instrument commands typically received from the PIs on the WIND instrument teams. The software needed to be tuned to handle the higher volume of POLAR instrument command files.
This article includes statistical information that shows the current reliability of the system, the breakdown of the POLAR commands by instrument and filetype, and the total number of commands per week for WIND and POLAR.
For speed and reliability, the analysis was based on WIND and POLAR files received since Feb 22, 1996. Out of 1130 files received, 1078 (95.4%) were processed automatically.
Of the 52 failures, 43.3% resulted from failure of the PI teams to follow the formats described in the Interface Control Document (ICD) between PIs-SPOF-CMS, 26.9% resulted from setup errors by the SPOF staff when rebooting/ restarting, 23.1% from a bug in the SPOF software now being corrected, and 7.7% from transient network failures. The mean length of time it took for one transmission to be processed was 3 minutes 3.6 seconds, with a standard deviation of 140.2 seconds.
Figure 1
The number of commands processed for POLAR is shown in figure 1. This chart shows the total number of each filetype by instrument. The volume of WIND commands for the same period beginning Jan 01, 1996 is approximately one-third that of POLAR at 267 commands. The bulk of the WIND commands files were sent in by the WAV (56%), 3DP (28%), and SWE (12%) instrument teams. The rest of the WIND command files (4%) were sent in by the other WIND instrument teams.
Figure 2
The graph in figure 2 shows the number of command files received per week for both the WIND and POLAR spacecrafts since the week ending Jan 25, 1996. The red bars show the quantity for WIND and the green bars show the quantity for POLAR. This chart graphically depicts the considerably larger volume of commands per week for the POLAR spacecraft.
The reliability of the SPOF command processing system has continued to increase in recent weeks as the SPOF staff have refined procedures to ensure correct setup and have corrected the software bug. As the PI teams become sensitized to ICD issues, this source of failure has also decreased.
The SPOF's design goal of 99.9% reliability seems to be achievable with continued effort to make the system more robust against transient network failures.
Chris Raymond
Computer Sciences Corp.
Goddard Space Flight Center
Mail Stop 694.0
Greenbelt, Md. 20771
raymond@spof01.gsfc.nasa.gov
Bruce Samuelson
Computer Sciences Corp.
Goddard Space Flight Center
Mail Stop 694.0
Greenbelt, Md. 20771
samuelson@spof01.gsfc.nasa.gov
Mauricio Peredo, Scott Boardsen, Daniel Berdichevsky and Greg Galiardi
With the transition to nominal POLAR operations, the Science Planning and Operations Facility (SPOF) has reached full speed support for the ISTP initiative. In recent months, the SPOF has greatly increased the number of services and products offered via its world wide web (WWW) server. The SPOF home page may be found at URL http://pwg.gsfc.nasa.gov. This communication highlights some of the new capabilities and services available to the ISTP and general space physics communities.
Figure 1
First of all, in collaboration with the Space Physics Data Facility (Code 632 at GSFC), a web-based interface termed "gif_walk" was developed to facilitate access to the standard SPOF orbit and Key Parameter survey plots. The gif_walk utility presents the appropriate plots with pull down menus to change amongst plot types, and type in fields to modify the date (in YYDDD or YYMMDD formats) of the plots to be displayed. Figure 1 contains a sample display of the gif_walk interface. Five different types of orbit plots are available, as well as 6 distinct families of Key Parameter survey plots. Additional plot types will be added in the near future for new POLAR-specific products. GIF files avalable on the web are available via anonymous ftp (also on the pwg.gsfc.nasa.gov machine).
Figure 2
Two other major areas of activity associated with POLAR operations revolve around the POLAR DeSpun Platform (DSP) pointing plan and the coordination of operations during Science Priority Operations Topics (SPOTs). A family of web pages (accessible from the SPOF homepage by following the "POLAR Despun Platform Pointing Plan" link) has been developed specifically for dissemination of information on the DSP pointing plan and its associated implications for the operation of the platform instruments (UVI, VIS, SEPS and PIXIE). These pages contain information on the operational constraints for the DSP as well as current DSP operational schedules. A number of custom plots are available to provide information about the plan and its implication on the viewing geometry. Snap shot images, such as the one in Figure 2, show the Earth, as seen from POLAR's location, with VIS and UVI field of views. The snap shots appear at 1 hour intervals, and each plot covers one half -day.
A separate collection of web pages provides access to the SPOTs information. These pages (accessible from the SPOF homepage by following the "GGS Science Priority Operations Topics" link) provide information on planned SPOT activities, as well as allowing community members to propose their own SPOTs by filling a web-based form. Any member of the world-wide space physics community can submit a request for a special SPOT activity, indicating what special operations are required from the instruments on ISTP spacecraft, or from collaborating ground-based or theory investigations. Submissions are made by filling out a web-based form page where users can specify the goals and requirements for their proposed special operations. SPOTs are reviewed by the appropriate ISTP project scientist(s) and if approved, entered into the plan and coordinated by the SPOF.
Another application for community-wide use is the GGS Event Catalog (accessible from the SPOF homepage by following the "ISTP/GGS Science Event Catalog" link). A mechanism has been implemented whereby a scientist who has identified a candidate event period, either from review of ISTP Key Parameter data or from other data, may fill in a web-based form proposing the interval in question as an event period. These proposed intervals will be presented at subsequent ISTP science working group meetings. When an interval is approved, the appropriate PIs pledge delivery of the necessary high resolution data (in CDF format) to carry out the event study, and the interval is entered into the Event Catalog. The proposing scientists must commit to maintain a web page for the interval in question (the SPOF provides a template for such event web pages), and to lead the analysis effort.
In addition to the new services detailed above, other enhancements to the ISTP web services, many of them based on community feedback, are under development. A key one is the development of a "Roadmap to ISTP web pages," which we expect to deploy in the coming weeks. As always, comments and suggestions are welcome, and may be addressed to Mauricio Peredo at peredo@istp1.gsfc.nasa.gov.
Mauricio Peredo
peredo@istp1.gsfc.nasa.gov
Scott Boardsen
boardsen@nssdca.gsfc.nasa.gov
Daniel Berdichevsky
berdi@istp1.gsfc.nasa.gov
Raytheon STX Corporation
Goddard Space Flight Center
Mailstop 632.0
Greenbelt, Md. 20771
Greg Galiardi
Goddard Space Flight Center
Space Physics Data Facility
Code 632
Greenbelt, Md. 20771
galiardi@nssdca.gsfc.nasa.gov