3rd IAASS international space safety conference
'Building a Safer Space Together'
Rome, Italy, 21-23 October 2008
WORLDWIDE SCIENTIFIC OPTICAL NETWORK
AS A GLOBAL SPACE SURVEILLANCE DATA SOURCE
Agapov, V.M.(1), Molotov, I.E.(1)
(1) Keldysh Institute of Applied Mathematics,
Russian Academy of Sciences, Russian Federation
ABSTRACT
The international scientific optical network (ISON) is collaborating with teams in 19 observatories around the world operating 24 telescope with aperture in range between 0.2 and 2.6 m. Now it represents one of largest ground systems specialized in observation of space debris and other objects on high geocentric orbits. It is capable to observe the whole GEO ring. The ISON performance had been constantly improving during the last 3 years of operations. The network have demonstrated capability to produce significant amount of high quality and often unique results in the field of space surveillance of high altitude (though mainly GEO for a while) orbits population of artificial objects. There are 152 bright (9th - 15th magnitude) and more than 430 faint (fainter than 15th magnitude) earlier unknown objects in GEO region discovered, including ones having high area-to-mass ratio (AMR). Thus population of continuously tracked objects in GEO region is increased more than 35 per cent comparing to the available public sources of space surveillance data. As many as 725000 positional measurements are accumulated already in the Center on collection, processing and analysis of information on space debris (CCPAISD) of the Keldysh Institute of Applied Mathematics (KIAM) for more than 1800 objects. Another research has started recently with the ISON new instruments. This is studying of the objects on HEO orbits of various classes (GTO, "Molniya" etc.). Number of discovered earlier unknown objects in HEO and GEO regions have exceeded 700 and regular tracking have established for the most part of them. The ISON is an open international non-government project and can be considered as a source of information on space objects for global civil space situation awareness (SSA) system.
1. INTRODUCTION
Unlike of other large space surveillance systems, the ISON [1] begun as completely civilian scientific project when it was initiated by KIAM of the Russian Academy of Sciences. Initially it was a project aiming to establish regular observations of the GEO region in order to obtain enough data to confirm the theory of evolution of fragment clouds created in explosions of old GEO resident objects [2]. Another goal was to support radar experiments [3] with additional tracking data needed for determination of orbital parameters precise enough to properly point narrow radar beams to selected objects. These researches were started by KIAM in 2001 and initiated the efforts on creation of the dedicated civilian global optical network - ISON.
From one side, ISON is a non-government project, and therefore do not have special state budget support, from the other side ISON is a voluntary union of astronomical observatories and scientific institutions, and therefore the financial expenses on support of observers and other staff are not as large as in case of dedicated military installations working in on-duty mode. Most part of observatories is working with the ISON for pure scientific interests and has possibility to use telescopes and other scientific equipment provided by the project for solving the various scientific goals. Thus, the ISON provides capability to arrange common observation campaigns for asteroids and gamma-ray-burst researches. This circumstance allows to maintain the ISON activities with support of scientific grants and small contracts on the observations of space objects. For example, the ISON started routine observations of the GEO objects in 2005 with support of grants provided by the International Association for the Promotion of Co-operation with Scientists from the New Independent States of the former Soviet Union (FSU) - INTAS, and the Russian Ministry of education and science.
The quantity of involved optical telescopes and observatories is larger than it seems from the first look. But this approach gives to the ISON flexibility, increased weather independence and global coverage.
Main goal of the project during 2005-2007 was development of the system capable to improve our knowledge on pollution of geostationary orbit (GEO). This region was selected as the first one to study because, from one hand, GEO is representing unique part of the near-Earth space from the point of view of solving the various tasks (television and communication services, weather monitoring, data relay, etc.), and, on the other hand, it is a limited natural resource which requires preservation for future use so we definitely need to know what is happening there already. In 2008 the regular observations of objects at highly-elliptical orbits (HEO) of various classes (GTO, "Molniya" etc.) are also started.
In 2007 and 2008 the project was officially presented at the United Nations level at the 44th and 45th sessions of the Scientific and Technical Subcommittee (STSC) of the UN Committee on the Peaceful Use of Outer Space (COPUOS) [4]. By the current time known population of objects in GEO region is increased more than 35 per cent thanks to the work of the ISON network and it's partners (and for the first turn - Astronomical Institute of University of Bern). More than 150 unknown relatively bright GEO objects had been discovered as well as 120 unknown HEO (on different orbit types) objects and nearly 430 earlier unknown faint (fainter than 15m) GEO and GTO space debris fragments. Some of the results are publishing annually in issues of "ESOC Classification of Geosynchronous Objects" (see [5] as the most recent published one). Overall coordination of the ISON work as well as analysis of obtained results is performed by KIAM.
2. ISON STRUCTURE AND DEVELOPMENT STRATEGY
The ISON collaborates with 19 observing facilities operating 24 telescopes in 9 states - Bolivia, Georgia, Moldova, Russia, Spain (ESA), Switzerland (AIUB), Tajikistan, Ukraine, Uzbekistan. The geographic positions and names of the observatories cooperating within framework of the ISON project are presented at Fig. 1, and the used telescopes are listed in Tab. 1.
All the ISON activities are arranged in four supporting groups:
- electric and software engineering,
- optical and mount engineering,
- network development,
- observation planning and data processing.
The ISON telescopes are grouped in three subsets dedicated to tracking of different classes of the space objects - bright GEO-objects, faint fragments at GEO region, bright objects at highly elliptical (HEO) and low orbits (LEO).
Electric and software engineering group has developed:
- the time keeping hardware for precise determination of CCD frame capture moment, utilizing the trigger mode of the CCD shutter,
- full set of software modules for control of all telescope devices under common platform - GPS receiver (AccuTime module), CCD camera (CameraControl module), telescope mount (CHAOS module),
- Apex II software package for astrometric and photometric reduction of the CCD frames [6].
Optical and mount engineering group has developed:
- a set of dedicated telescopes for 3 ISON subsets,
- a set of mounts with different weigh capacity,
- lots of individual solutions (but utilizing common standards for control and tracking capabilities) for automation of the mounts of legacy telescopes that are working with the ISON.
Observation planning and data processing group develops standard observation modes for telescopes of the 3 ISON subsets - survey, search scan, ephemeris tracking etc., and adjusts new observations techniques with each observatory team.
Network development group plans the telescope upgrade, production of the new ones, purchasing CCD cameras for each of the ISON observatory to meet the requirements of observation techniques developed by the observation planning and data processing group. In the whole, 16 optical telescopes, 3 mounts and 30 time keeping devices are produced for the ISON project, and 26 CCD cameras and 7 mounts were purchased for equipment of the observatories collaborating with the ISON.
The ISON search and survey subsystem for studying of the bright (not fainter than 15.5m) objects in GEO region consists of ten 22-cm telescopes RST-220 and ORI-22 with the field of view (FOV) of 4° that are installed at Milkovo, Ussuriysk, Blagoveschensk, Kitab, Abastumani, Nauchniy-1, Nauchniy-2, Pulkovo, Tiraspol and Tarija [7]. In addition a few 25-cm telescopes will be used for follow up tracking of discovered unknown objects (the first GAS-250 telescope starts observations in October in Ussuriysk).
Subsystem for high altitude faint (15.5m to 20m) space debris fragments detection and tracking consists of the telescopes with aperture from 0.5 to 2.6 m and includes 2.6 m ZTSh and 64-cm AT-64 telescopes in Nauchniy-1, 70-cm AZT-8 telescopes in Gissar, 60-cm RC-600 telescope in Mayaki, 2 m Zeiss-2000 telescope in Terskol, 1 m Zeiss-1000 telescope in Simeiz, 70-cm AS-32 telescope in Abastumani and other. In addition few more telescopes will start observations soon - 60-cm S-600 in Andrushevka, 50-cm ORI-50 in Ussuriysk, 80-cm RC-800 in Mayaki. The negotiations about joining to the ISON project are in progress with several observatories having 0.6 m - 2m class telescopes in Bulgaria, Azerbaijan and Ukraine.
 Figure 1: Geographic location and names of the observatories collaborating with ISON. Red circles represent survey subsystem, green circles are locations of instruments for faint space debris observations, yellow circles represent European partners of the ISON, white circles - planned locations. Triangle represents CCPAISD at the KIAM RAS.
Table 1: Observatories and telescopes of the International Scientific Optical Network in 2008
and observing night/measurement statistics for each telescope in 2007 and 8 months of 2008.
| Observatory name | Telesc.name
and aperture, cm | CCD,
pixels | FOV | Lim. mag,
5 sec int. time, m | Mount
automation | Obs. nights quantity | Measurem. quant. |
|---|
| 2007 | 2008 | 2007 | 2008 |
| Pulkovo | RST-220, 22 | 3k*3k, 12 | 4° | 14 | full | 33 | 20 | 9485 | 12526 |
| Nauchniy-1 | ZTSh, 260 | 1k*1k, 24 | 8,4' | 20 | partial | 21 | 19 | 7127 | 6337 |
| AT-64, 64 | 4k*4k, 9 | 2,3° | 17 | full | 122 | 84 | 12840 | 26271 |
| RST-220, 22 | 3k*3k, 12 | 4° | 15 | full | 78 | 65 | 41880 | 67767 |
| Simeiz | Zeiss-1000, 100 | 1k*1k, 24 | 12.8' | 18.5 | partial | 17 | 9 | 3965 | 1721 |
| Zeiss-600, 60 | 1k*1k, 24 | 30' | 17 | full | under upgrade |
| Nauchniy-2 | RST-220, 22 | 4k*4k, 9 | 4° | 15 | - | - | 88 | - | 34829 |
| Tiraspol | RST-220, 22 | 3k*3k, 12 | 4° | 14 | full | 55 | 75 | 13081 | 16987 |
| K-360, 36 | 3k*3k, 12 | 1° | 15 | full | in production |
| Mayaki | RC-800, 80 | 3k*3k, 12 | 1° | 17.5 | full | production finished |
| RC-600, 60 | 1k*1k, 24 | 1.5° | 16.5 | full | 110 | 58 | 15309 | 6080 |
| Andrushevka | S-600, 60 | 3k*3k, 12 | 2° | 16.5 | full | test observations |
| Terskol | Zeiss2000, 200 | 2k*2k, 24 | 15' | 20 | partial | | 4 | | 1559 |
| K-800, 80 | 3k*3k, 12 | 1° | 18 | partial | test observations |
| Abastumani | AS-32, 70 | 3k*2k, 9 | 36.7' | 17 | partial | - | 5 | - | 380 |
| ORI-22, 22 | 3k*3k, 12 | 4° | 15 | partial | 87 | 30 | 12690 | 7525 |
| Kitab | ORI-40, 40 | 3k*3k, 12 | 2.2° | 16 | full | in production |
| ORI-22, 22 | 2k*2k, 24 | 5.5° | 15 | partial | 203 | 141 | 38646 | 58583 |
| VT-15, 12.5 | 2k*2k, 24 | 15° | 13 | full | test observations |
| Gissar | AZT-8, 70 | 1k*1k, 24 | 30' | 17 | partial | 28 | 72 | 3195 | 14695 |
| Krasnojarsk | ORI-40, 40 | 3k*3k, 12 | 2.2° | 16 | full | in production |
| Refractor, 15 | 3k*3k, 12 | 2° | 14 | partial | in installation |
| Blagoveschensk | ORI-22, 22 | 1k*1k, 24 | 2.6° | 15 | full | test observations |
| Ussuriysk | ORI-50, 50 | 2k*2k, 24 | 2.5° | 16.5 | full | production finished |
| GAS-250, 25 | 3k*2k, 9 | 1.7° | 15 | partial | - | - | - | - |
| ORI-22, 22 | 3k*3k, 12 | 4° | 15 | full | 115 | 117 | 15875 | 28405 |
| VT-15, 12.5 | 2k*2k, 24 | 15° | 13 | full | in production |
| Milkovo | ORI-22, 22 | 3k*3k, 12 | 4° | 15 | full | 2 | 45 | 279 | 11426 |
| Tarija | Zeiss-600, 60 | 3k*3k, 12 | 45' | 17 | full | under upgrade |
| Astrograph, 23 | 1k*1k, 24 | 35' | 14 | - | 54 | 56 | 10419 | 11194 |
| ORI-22, 22 | 3k*3k, 12 | 4° | 15 | full | in production |
Search and survey subsystem for studying the objects at HEO and LEO orbits will consists of 125-mm VT-15 lens objectives with FOV of 15°. The HEO objects will be observed during fast surveys of the sky, while LEO objects will be observed with fixed VT-15 objective - it is expected that each objective can obtain up to several hundred trails of LEO objects per night. First two VT-15 objectives will be installed in Ussuriysk and Kitab, and three more VT-15 will be produced the next year for Tarija, Tiraspol and Gissar. In addition, during 2009 a few 25-cm GAS-250 and 40-cm ORI-40 telescopes will be produced in order to provide follow up tracking of HEO and LEO objects. Some of the telescopes are shown on Fig. 2 and Fig. 3.
Since 2009 the ISON will have more than 35 telescopes from 12.5 cm to 2.6 m aperture grouped in three dedicated subsets that can perform observations of all bright (down to 15.5m) GEO-objects along 360 deg arc, search, discover and track the faint fragments down to 21m, track the most part of HEO-objects brighter than 15.5m and provide large volume of measurements for the LEO objects.
Figure 2. 2.6 m ZTSh, 64-cm AT-64 and 22-cm RST-220 telescopes in Nauchniy-1 (CrAO).
Figure 3. New 125-mm VT-15 objective, 50-cm ORI-50 telescope and it's mount for Ussuriysk.
3. STATUS OF THE ISON OBSERVATIONS OF SPACE DEBRIS
The ISON observations are coordinated mainly by the CCPAISD developed and operated on the basis of the Ballistic Centre at the KIAM, Russian Academy of Sciences. Since 2007 the observations are carried out almost each night with acceptable weather/moonlight conditions - 1042 telescope-nights are accumulated in 2007 and 927 telescope-nights are accumulated for 8 months of 2008. Observation statistics for each telescope for 2007 and 2008 is presented in Tab. 1. Measurement quantity growth rate is shown on Fig. 4. Overall statistics for 8 months of 2008 is given in Tab. 2.
One can see that the ISON continuously increases its performance - the quantity of measurements for 2007 is four times more comparing to 2006. Also, there are 330000 measurements in 41000 tracks along the whole GEO belt (360°) are obtained by the ISON during January-August 2008 that is almost two times more than in 2007.
CCPAISD already collected more than 725000 measurements for nearly 1800 space objects [8]. Currently ISON is capable to perform the observations of selected objects along the whole GEO belt (360°), near GEO belt (±2°) surveys for the arc 130.3W - 210.6E, wide (±16°) surveys of the GEO region for the arc 30W - 90E with the goal of discovery of all objects brighter than 16m, as well as to search (limiting magnitude 19m) and track (limiting magnitude 21m), objects (including faint space debris) on GTO and other HEO orbits, photometry of tracked objects.
Figure 4. Statistics of the ISON measurements from 2003 to 2008 years for the all measurements (upper line) and measurements for faint fragments only (bottom line)
Table 2. ISON observation statistics for January-August 2008
| Parameter | January | February | March | April | May | June | July | August |
| Observing nights | 30 | 28 | 31 | 29 | 31 | 30 | 31 | 31 |
| Quantity of tracks | 7077 | 5212 | 4858 | 4838 | 4826 | 5294 | 3602 | 4053 |
| Common duration of all tracks (hours) | 1627 | 2402 | 872 | 899 | 925 | 908 | 552 | 899 |
| Average duration of a single track (min) | 14 | 15 | 11 | 11 | 11 | 10 | 9 | 13 |
| Quantity of measurements | 49053 | 39751 | 34391 | 42750 | 48880 | 55568 | 35717 | 38932 |
| Average quantity of measurements in a single track | 7 | 8 | 8 | 9 | 10 | 11 | 10 | 10 |
| Quantity of observed space objects | 1200 | 972 | 1008 | 1060 | 1064 | 1051 | 824 | 961 |
| Covered GEO arc (degrees) | 330 | 228 | 360 | 360 | 360 | 360 | 360 | 360 |
4. THE ISON OBSERVATIONS PROCESSING RESULTS
Number of objects in GEO and HEO that are continuously tracked by the ISON is now exceeds 1800, including 152 unknown bright GEO objects (brighter than 15m) and 120 unknown bright HEO objects. 434 faint (fainter than 15m) GEO and GTO objects are discovered in GEO region surveys during the last 3 years, including objects with high AMR. Of this number, 192 faint GEO objects are tracked continuously. So, thanks to the ISON and it's partners population of known continuously tracked objects in the GEO region is increased by more than 35 per cent [9].
Presence of space debris clouds created in earlier suspected fragmentations of GEO objects is proved not only by statistical observation approaches but for the first time - by long deterministic observations of individual members of the clouds. For the first time, a large amount of data on long time intervals is obtained for objects with high AMR. Both observational and orbital peculiarities of these objects are revealed and studied. Figures shown hereafter represents some of results obtained by the ISON during 3 years of work.
Fig.5 to Fig. 10 represents distributions of the objects discovered by the ISON by brightness, AMR value and some orbital parameters.
One can see that the most part of 434 fragments included into the brightness plot (Fig. 5) is concentrated around magnitude range of 16m to 18m. This picture reflects rather current observation capabilities of the ISON then real distribution of existing population of space debris in GEO region. Fainter objects are much hard to discover and track especially taking into account high brightness variability of many of them. Large aperture sensitive instruments are required for this goal. The ISON primary instruments at present are mid-class telescopes (with aperture up to 0.8 m) so one can expect that involvement of additional larger aperture telescopes into the project will significantly change the distribution for fainter objects.
Figure 5. Distribution of average brightness for 434 fragments discovered by the ISON
Distribution of AMR values for fragments (Fig. 6) is constructed taking into account only those of discovered debris objects for which full 6 orbital parameters vector was obtained and amount of measurements and length of a measurement distribution arc (by time) was enough to estimate the AMR value as an additional parameter. Only 211 of 439 discovered fragments are satisfied these criteria. For other fragments the measurement distribution arc is too short in order to reliably determine AMR value or even full 6 parameters orbit vector. The nature of objects with AMR larger than 1 sq.m per kg is not clear yet. Dominating hypothesis is that objects formed of a multi-layer insulation (MLI) pieces which are separating from a spacecrafts under influence of space environment conditions.
Figure 6. Distribution of average AMR value for 211 fragments discovered by the ISON
Fig. 6 and Fig. 7 represent distribution of orbital parameters for only those of discovered debris objects for which reliable full 6 orbital parameters vector is obtained even in case when AMR value is not estimated. High AMR objects location on these diagrams is depicted by ellipses.
Figure 7. Distribution of eccentricity and semi-major axis for 336 fragments discovered by the ISON
Fig. 9 shows distribution in RAAN-Inclination space of all objects in GEO continuously tracking at present. It is interesting that the ISON work resulted in discovery of many objects in GEO region having orbital plane parameters significantly different of those objects for which orbital data are provided officially by the U.S. Space Surveillance Network (SSN). Many of these objects can be associated with some of the U.S. military GEO launches. They are mostly bright and easily detectable even by amateur astronomical instruments. One can see from this figure that discovered space debris fragments are forming 'clouds' that makes possible to suppose several fragmentation events as their origin source.
Figure 8. Distribution of apogee and perigee for 336 fragments discovered by the ISON
Figure 9. Distribution of 1309 GEO objects tracked by the ISON including 152 bright (blue circles) and 192 faint (red circles) GEO objects discovered by the ISON and partners, and 965 objects with orbits provided by the US SSN (green dots) by RAAN and inclination (early Jul, 2008)
At last, Fig. 10 shows one of results obtained recently. It represents distribution of newly discovered objects on various high elliptical orbits (HEO), mainly GTO and Molniya-type. These are bright (thus, supposedly large) objects so their discovery is another confirmation of incompleteness of currently available space surveillance data even for larger objects on elliptical orbits.
Preliminary analysis shows that the most part of newly discovered objects on elliptical orbits can be associated with launches performed from Kourou (inclinations 4°-8°), Cape Canaveral and Xichang (inclinations 25°-29°) on GEO-transfer orbits (GTO). Another group of objects with inclinations close to 63.4° is related to the U.S. and Russian launches on Molniya-type semi-synchronous obits. Of course, it is possible that some of discovered objects on HEO are related to known and yet unknown explosions of upper stages occurred in the past.
Figure 10. Distribution of 120 new bright HEO objects discovered by the ISON by period and inclination
5. CONCLUSIONS
Started in 2001 the ISON project is significantly expanded by the current time. Now it already joins 19 observatories and observation facilities around the world. Overall work of the ISON is coordinated by the Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences.
The ISON network at present is the only civilian non-governmental one which is capable to produce significant output in area of space surveillance of the higher Earth orbits which can be used for various purposes including scientific research of space debris problem as well as space situation awareness in the interests of commercial and other civilian spacecraft operators. The output produced by the ISON by it's quality and quantity is comparable if not exceeds in some points similar data producing and officially distributing by the most powerful space surveillance system in the world operated by the U.S. Air Force. By now the ISON have discovered more than 700 new objects on high geocentric orbits.
The ISON represent first in the world civilian global space surveillance system covering whole GEO and capable to search and track objects both on GEO and various classes of HEO orbits (GTO, Molniya etc.). The ISON work significantly improved our knowledge of the real situation in GEO region. Thanks to the conducted research the number of continuously tracked objects in this vital near-Earth region of space increased 35%. Number of newly discovered objects continues to grow.
Another important thing demonstrated by the ISON is possibility of very fruitful and successful cooperation between researchers in many countries within framework of very complex program of the near-Earth orbital population studying.
Thus the ISON can be considered as a proof of organizational, financial, technical and practical feasibility of civilian SSA system.
ACKNOWLEDGEMENTS
We appreciate the work performing by the staff of the observatories in Zimmerwald, Tenerife/Teide, Nauchniy, Pulkovo, Mondy, Maidanak, Kitab, Ussuriysk, Terskol, Simeiz, Tiraspol, Tarija, Abastumani, Mayaki, Gissar, Milkovo, Yevpatoriya, Arkhyz and Andrushevka that participated earlier or continuing to participate in the ISON observation program.
Authors thanks also Vladimir Kouprianov and Irina Guseva in Pulkovo observatory for the development of the CCD frame standard processing software and training support at the ISON observatories.
The ISON project would not be so efficient without excellent work of Valery Terebizh and Gennady Borisov who developed and produced survey telescopes.
REFERENCES
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