PROCEEDING OF THE 4 TH SOUTHEAST ASIA ASTRONOMY NETWORK MEETING, BANDUNG 1-11 OCTOBER 212 Editor: D. Herdiwijaya DEBRIS IMPACT ON LOW EARTH ORBIT SPACE MISSION DHANI HERDIWIJAYA Astronomy Research Division and Bosscha Observatory, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Ganesha 1, Bandung, Indonesia 4132 Email: dhani@as.itb.ac.id Abstract. Earth orbiting spacecraft have become an integral part of our everyday lives. We depend on them for communications, weather information, scientific research, and national security. A real and growing concern for the safety and reliability of these satellites is the threat from collision with other orbiting objects including space debris or their reentry processes. The orbital debris environment is a growing concern for operational spacecraft, in both the low and geosynchronous orbit regimes. The LEO and GEO environments have over 1, objects with a size of 1 cm or larger. These objects include operational (functional) spacecraft, non-operational (inactive or retired) spacecraft and rocket bodies, as well as debris from a variety of sources. We used Debris Assessment Software which has complied with NASA Technical Standard 8719.14, as a standar tool, to figure out the evolution of debris and uncontrolled reentry demisability analysis process, especially for LEO space mission, like Indonesia LAPAN s satellites. 1. INTRODUCTION The first Indonesian telecommunication satellite was launched in 8 July 1976. However, the global increasing number of telecommunication satellites is significant enough to have government and related industry predicted about the increased collision hazard among satellites. A real and growing concern for the safety and reliability of these satellites is the threat from collision with other orbiting objects including space debris. Even a tiny particle can damage or degrade satellite due to the very high velocities involved in a collision, on the average about 11 km/sec. Generally, a satellite reentering the Earth s atmosphere will break up and only very large space structures and those satellites containing radioactive or other toxic materials are deemed significant threats. Factors that affect satellite breakup and debris survivability are initial speed, flight path angle, melting temperature of components, and the ballistic coefficient of the primary body and the subsequent pieces. Since survivability directly affects casualty expectation, space mission planners need a reliable prediction capability to decide whether random reentry is acceptable. If casualty expectation is too large, controlled reentry should be considered. Moreover, as the satellite population increases so do the debris and then associated random reentries and risk to people and property. The growth in global population further in- 36
Debris Impact on Low Earth Orbit Space Mission 37 creases the casualty expectation and adds urgency to the satellite debris reentry hazard problem. The easiest method of deorbiting a satellite is to lower the perigee altitude such that atmospheric drag causes the satellite s orbit to decay, and the spacecraft to reenter in a random fashion. Some spacecraft plan to use low-thrust motors as propulsion systems to lower perigee altitude. However, it is not provide sufficient impulse to allow targeting the spacecraft to a specific reentry point (Reynolds and Eichler, 1997). A major unknown condition is the lack of knowledge of exactly where on Earth the object will actually touch down. Even during the last orbits, predicting the exact orbital revolution in which reentry occurs is difficult. This uncertainty is in the time of reentry, which means that a 1-minute error corresponds to approximately 4,5 km of uncertainty in the impact point. Thus, warning to dense population area of an impending reentry is virtually impossible (Janin and de Leeuw, 1985). For limiting the risk of human casualty, NASA requires the limit of impact energy should less than 15 joule and risk of humas casualty for surviving debris should not exceed.1 or 1 in 1, people. This paper will analyse the Indonesian satellites in LEO orbit, that are LAPAN TUBSAT, LAPAN A2, LAPAN ORARI and TELKOM 3, in order to check whether they fullfill two items of the NASA Technical Standard 8719.14 Requirement, that are Section 4.6 for Post Mission Disposal of Space Structure and Section 4.7 Survival of Debris from the Post Mission Disposal Atmospheric Reentry Option. The first of three satellites is microsatellites for Earth observations and remote sensing purposes. The last satellite was a failed GSO satelite for communications. For doing this study, we explore the standard tool, NASA Debris Assesment Software version 2..2, NASA Ordem2 and ESA Spenvis. The Two-Line Elements of those satellites are obtained from http://www.space-track.com/ in which element orbit can be generated. 2. ORBITAL ELEMENTS LAPAN-TUBSAT micro satellite is a first Indonesian satellite which jointly developed by LAPAN and Technische University Berlin engineers. LAPAN-TUBSAT micro satellite has unique mission strategy. The agility of the micro satellite made it possible for surveillance of object in which the location is not pre-defined because its attitude and camera pointing can be manipulated off-nadir and controlled interactively. The structure of the satellite was made of Aluminum Alloy (Al alloy 224 T351) and stainless steel, and painted black anodized for thermal characteristic purposes (Triharjanto et al. 24; Hardhienata et al. 25). The second generation twin satellites, LAPAN A2 and LAPAN ORARI are planned to launch in year 213. LAPAN A2 will carry AIS (Automatic Identification System) to identify the ships in the waters of Indonesia and a video camera three times wider than the Lapan-Tubsat for resolution 8 km and 6 m ground resolutions. LAPAN ORARI is a microsatellite for disaster management by amateur radio communication (ORARI), as well as Earth observation (multi-spectral remote sensing) for land use, natural resource and environment monitoring. LAPAN-ORARI carries a payload of voice repeaters and an APRS Repeater. The TELKOM 3 satellite was built by ISS Reshetnev with a communications payload provided by Thales Alenia Space. The $2 million satellite's 42 C-band and
38 Herdiwijaya Ku-band transponders were to be operated by Telkom for broadcast and data transmission services in 15 years long. The satellite has been placed in a wrong orbit by a Proton-M Russian launcher. We estimate its size, since no information available. The generated element orbits for LAPAN TUBSAT and TELKOM 3 satellites and their pre-launch dimension are tabulated in Table 1. The apogee of TELKOM 3 satellite is higher than 2 km and its perigee is very low at about 27 km altitude. It is an unusual altitude that will shorten its lifetime. Table 1. Orbital elements of LAPAN and TELKOM satellites (per at 1 October 212) Satellite Data LAPAN LAPAN A2 and TELKOM 3 TUBSAT LAPAN ORARI Catalog Number 2979-38744 Launch Date 27-1-1 (213) 212-8-6 Period (min) 97.25-14.8 Inclination (deg) 97.6536 (8) 49.9 Apogee (km) 637.182 (65) 4918.2 Perigee (km) 619.715-27.5 RAAN (deg) 35.47-126.846 Arg. of Perigee (deg) 317.354-18.285 Mean Anomaly (deg) 12.453-281.57 Eccentricity.1247 -.25925 Mass (kg) 56 78 193 Size (cm) 45x45x27 5x47x38 (6x25) Shape box box cylinder 3. DEBRIS IMPACT Figure 1. The number of impact and debris diameter in cm with a logaritmic scale. Orbital altitude contours are in 2 km (line-diamond), 6 km (bold line), 1 km (line-cross) and 15 km (line-circle) altitudes. The used debris database in DAS 2 is comparable with other catalog in which the densest region located between 8-9 km altitudes. Another dense region is on range 14-15 km altitude. The LAPAN satellites at about 6 km have a higher collision probability with space debris. On the other hand, TELKOM 3 satellite lo-
Debris Impact on Low Earth Orbit Space Mission 39 cated in region with a lower impact probability. However, its large cross section will increase the rate of collision. 4. HISTORY OF APOGEE AND PERIGEE ALTITUDE By using satellite elemen orbits (see Table 1), we can contructed the evolution of satellite orbit. Figure 2 shows that the lifetimes of LAPAN TUBSAT and TELKOM 3 are 47.562 years and 13.257 years, respectively. The area to mass ratio of TELKOM 3 is assumed to be.1 m 2 /kg. Both satellites will decay as disposal by atmospheric reentry by year 254 and year 225 for LAPAN TUBSAT and TELKOM 3, respectively. Figure 2. The orbital evolution of LAPAN TUBSAT (left) and TELKOM 3 (right). The higher and lower curves are apogee and perigee altitudes, respectively. During the atmospheric reentry processes, some materials could not be fully ablated in which they can cause human casualty when impacting to dense population region. Kinetic Energy (Joule) 1 8 6 4 2.5 1 1.5 2 Aluminum Mass (kg) Figure 3. The kinetic impact energy as function with aluminum mass of Al 224 T351 with box shape (left) and cylinder shape (right). Fully Ablate Altitude (km) 8 6 4 2 Fully Ablate Altitude (km) Stainless Steel Steel A-286 5 1 15 2 25 Mass (kg) 2 4 6 8 1 Figure 4. Fully ablate altitude as function with material mass of stainless stell and steel A-286 8 6 4 2 Aluminum Mass (kg)
4 Herdiwijaya In Figure 3, by assuming box shape of LAPAN TUBSAT satellite, the impact energy is larger than 15 Joule for.5 kg in aluminum mass that cause 1 m 2 casualty area. Changing to the cylinder shape, satellite will fully ablate or no casualty in altitude less than 8 km for aluminum mass between.5 to 87 kg. It is better alternative geometric shape. This satellite also consists of stainless steel material. In Figure 4, the lighter stainless steel mass of 3 kg will cause 1 m 2 damage area. However, increasing mass will have no casualty, since it will fully ablates in higher than 4 km altitude. Considering another type of material, e.g. steel A-286, the altitude of fully ablates is higher than stainless steel. It means that steel A-286 is better than using stainless steel. Steel A-286 is one of the most popular high temperature alloys where high tensile strength, excellent creep strength and good corrosion resistance are required. 5. CONCLUSION LAPAN Tubsat will be reentered in year 254 or 47 years later which is not comply with NASA Standard which requires lifetime no more than 3 years after launch for atmospheric reentry option. It will also cause casualty area of about 1 m 2, since impacting kinetic energy larger than 15 Joule. In the future, changing to the cylinder shape and steel A-286 will make zero casualties space mission. Due to very low perigee altitude, TELKOM 3 satellite will follow atmospheric reentry and trigger casualty area larger than 1 m 2. It is suggested that TELKOM 3 satellite should use most of its fuel to change its trajectory to put into storage orbit at perigee altitude larger than 2 km. Acknowledgments. This work has been supported by Institute Technology of Bandung Research Grant No. 41/l.1.C1/PL/212. REFERENCES Reynolds, R and Eichler, P., Options for Postmission Disposal of Upper Stages, IAA-97- IAA.6.5.2, 48th International Astronautical Congress, Oct 1997, Turin, Italy. Janin, G and de Leeuw, J., Decay of ESA Space Objects, Proceedings of Workshop on Reentry of Space Debris, p. 75, Darmstadt, FRG, Sept 1985. Triharjanto, H. R., Hasbi, W., Widipaminto, A., Mukhayadi M., Renner, U. LAPAN-TUBSAT: Micro-Satellite Platform for Surveillance & Remote Sensing, Proceedings 4S Symposium-Small Satellites, System and Services, Paris, 24. Hardhienata, S., Nuryanto, A., Triharjanto, H.R. and Renner, U., Technical Aspects and Attitude Control Strategy of LAPAN-TUBSAT Micro-Satellite, LAPAN- Technische Universität Berlin, 6th International Symposium of the International Academy of Astronautics (IAA), Berlin, 25.