Center for Space Debris Data Collection, Processing and Analysis
Keldysh Institute of Applied Mathematics (KIAM)
Russian Academy of Sciences
4 Miusskaya Sq., Moscow, 125047 Russia
High Geocentric Orbit Space Debris Circular No.4
Coverage period ends on May 1, 2007 12:00 UTC
Editor: Vladimir Agapov
This circular opens a new series of publications devoted to periodically summarizing the worldwide scientific activities in observations of space debris objects on high geocentric orbits (GEO, HEO and high near-circular non-GEO). Objects considered to be included into this publication are fragments (operational by nature, created in fragmentation events or as a result of larger objects’ surface and construction deterioration due to environment conditions) having brightness fainter than 15th visual magnitude during most part of their observation time. This limit corresponds to approximately 1 m size object on geostationary orbit. It is possible that sometimes these objects can be brighter than 15th magnitude due to combination of their specific properties (surface reflectivity and attitude) and favorable observation conditions (good phase angle, high elevation etc.).
The goal of this publication is to give the world scientific community imagination about the status of high geocentric orbit space debris researches and to provide up to date data for each discovered object including orbital parameters, estimated standard magnitude and estimated area-to-mass ratio value. Those data can be included in existing space debris models as well as can be used for study of long-term orbital evolution and possible origin of the objects. The Circular will also serve as some reference document for scientists and amateurs involved in those objects observations and data analysis. Operators of spacecraft in high geocentric orbits (mainly in GEO) can use this publication in order to obtain a more realistic description of the situation around their orbital assets.
Observation planning, ephemeris support, processing and analysis of obtained data are made by researchers from Keldysh Institute of Applied Mathematics (KIAM) (Vladimir Agapov, Igor Molotov, Viktor Stepanyants, Vladimir Titenko) with invaluable help of Zakhariy Khutorovskiy (Vympel Corporation) and Vasiliy Yurasov (Institute for Precision Instrument Engineering, IPIE).
The presented results include discoveries stemming from surveys of the European Space Agency (ESA) utilizing the ESA Space Debris Telescope in Tenerife. Those surveys and all follow-up observations from the ZIMLAT telescope of the Astronomical Institute of the University of Bern in Switzerland (AIUB) are planned, run, processed, and analyzed by the AIUB.
All questions regarding cooperation in the joint research program for high geocentric orbit space debris studies should be sent to Prof. E. L. Akim, KIAM Deputy Director. All questions regarding observation schedule, required formats, ephemeris support, observations and orbital data processing, analysis and usage should be sent to Dr. V. M. Agapov. All questions regarding requirements for observation instruments, CCD frame processing software, possible help in the instrumentation upgrade in order to make possible participation in the research program should be sent to Dr. I. Ye. Molotov.
List of sensors
This list includes all sensors participating today in a joint program of observation and analysis of space debris objects on high geocentric orbits. Each sensor has its own identification number assigned in the KIAM space objects database. Most of the sensors are involved in minor planet observations as well, thus having the MPC-assigned identification code. But for the purpose of this research program it was decided to maintain a separate ID system permitting to describe all participating sensors regardless of their involvement in other research programs. Coordinates of sensors are given for reference purposes only and should not be used in real observation processing. In the column “Instrument”, the common name, aperture (d, mm) and focal length (f, mm) of each instrument are given.
The list will be updated each time a new sensor will send observations for objects studied.
Table 1. List of participating sensors
This section contains information on the objects newly discovered during the period Apr 1-Apr 30, 2007.
There are two lists. The first one contains information on objects which have been successfully recovered in follow-up observations after initial detection and one-night tracking and for which orbital data and area-to-mass ratio (AMR) value have been determined with high level of confidence. The second one contains information on objects having only one-night track of observations. A complete set of orbital data cannot be determined for these objects. Only some orbital parameters (mainly inclination and RAAN) are determined relatively accurately. The AMR values cannot be determined for these objects at all.
It should be noted that all one-night tracks have been tested to identify them with all other one-night tracks and with all known objects in the KIAM database having well determined orbits (both bright and faint). It is possible that the identification failed not only due to the absence of other tracks of the same object, but also due to uncertainty caused by an unknown AMR value which can result in very significant orbital evolution that prevents proper correlation of one-night tracks.
Each object listed in this section has two identifiers. The first one (column ID2 in the table below) is assigned by the observer who discovered the object and the second one (ID1) is assigned in the KIAM space objects database. Since no commonly agreed space debris identification system exists yet all identifiers provided can be regarded as temporary ones. As soon as such a system will be agreed upon, all objects will be assigned with the new identifiers.
Orbital elements are referring to True Equator Mean Equinox (TEME) coordinate system. Area-to-mass ratios are calculated assuming reflectivity coefficient equal to 1.3. Orbital elements for short tracks (Table 3) are obtained in two steps. In the first step an attempt is made to determine an orbit with zero eccentricity. In case of large residuals (more than the expected 3- sigma) the second step is applied. At this step the eccentricity is also estimated.
There are 9 new objects discovered and subsequently confirmed in April. Also 9 more new objects are discovered but observed only on short tracks on one night only.
Table 2. List of newly discovered and confirmed objects
Of the nine objects discovered in April two are the very interesting ones namely 43130 and 90054.
The first one have very large AMR value - of order of 30 sq.m/kg, but relatively good predictable motion indicating very small variations of the AMR value. At the moment of this issue compilation the object was still tracking without problems and without involving special search strategies. It's eccentricity is increasing at present and if it will not be lost during the next two months then we will have continuous real orbital data for such kind of objects precise enough to involve radars for studying of it's properties.
The second object, 90054, is the unique one due to combination of the high AMR value (near 3.2-3.3 sq.m/kg in average) and the enormous (for objects of this class) brightness observed during routine tracking of it. On some intervals up to 20 minutes long the brightness was increasing up to magnitude in 9m-10m range making it comparable to the one associated with the largest satellites orbiting GEO. It was continuous brightness increasing not short time flashing of flaring which is common for many GEO objects especially during the eclipses season. One can assume that the object is some kind of a 'prefect' mirror-reflector having slow attitude motion and producing 'continuous flares' from time to time. Thanks to such strange the brightness pattern it was possible to observe the object even with small instruments having aperture 22 cm or even less. It is interesting also that at the time of the discovery the orbital plane of the 90054 perfectly matches the orbital plane of the retired GEO satellite 20570/1990-034A PALAPA B2R (within 0.01 deg both in inclination and RAAN) though analysis doesn't reveals any close encounters between these two objects at least in 2007.
Table 3. List of newly discovered objects having only single one-night track of observations
This section contains information on successful identification of newly and previously obtained single one-night tracks with each other as well as with objects having well determined orbits.
Table 4. New identifications
This section contains information on the latest orbital updates for objects discovered prior to Apr 1, 2007 and observed at least once in Apr 2007 or for which the latest orbital update was not published in the previous issues. 42 of previously discovered objects in total are observed in Apr 2007.
Table 5. Updated orbital parameters for objects observed in Apr 2007.
Master list of objects
The master list of objects includes all high altitude orbit faint objects discovered up today, with a description of the circumstances of the discovery and the last update of orbital information. Due to the large volume of the master list it will be distributed separately in electronic form only.
This section contains general statistics on obtained measurements.
9 facilities have observed high altitude space debris objects in Apr 2007. The weather in April was slightly better than in March in all facilities though very unstable. Overall number of observation nights increased. Number of the observation facilities worked during the same calendar night was following:
Table 6. Distribution of measurements obtained by each facility by year of observation (as of May 1, 2007 12:00 UTC)
Table 7. Observation statistics for Apr 2007
In the previous issue the second column of the table was named 'Number of observed earlier discovered objects' but the figures showed for the different facilities were different in meaning due to different counting approaches that resulted in some misunderstanding in the overall number of the observed objects. Number of the new discovered objects was excluded from the count showed in the 'Number of observed earlier discovered objects' column for those facilities which discovered the objects though these the new discovered objects were in fact counted for the facilities observed them in the follow-up sessions. Thus the real total number of objects observed by the each facility was not clear.
To avoid the problem of the observation statistics interpretation the column is renamed to 'Total number of observed objects' and all counts are appropriately corrected by means of counting of all observed objects. So, the column 'Number of new discovered objects (including later confirmed)' now reflects only discovery statistics and should not be used for obtaining of the total count of observed objects.
We would like to express our appreciation to Rudiger Jehn (European Space Operations Center), Vladimir Kouprianov (Pulkovo Observatory), Vasiliy Rumyantsev (Crimean Astrophysical Observatory), Thomas Schildkneht (Astronomical Institute of the University of Bern) and Vasiliy Yurasov (Institute for Precision Instrument Engineering, IPIE) for their comments and suggestions aimed to the Circular improvement.
4 èþëÿ 2007.