Evaluation of the 27 March 2019 Indian Asat Demonstration
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AAS 19-942 EVALUATION OF THE 27 MARCH 2019 INDIAN ASAT DEMONSTRATION Andrew J. Abraham* On 27 March 2019 India announced the successful demonstration of a Direct As- cent Anti-Satellite (DA-ASAT) weapon. India claims their Kinetic Kill Vehicle hit Microsat-R and destroyed it in a responsible manner that limited the debris cloud lifetime to 45 days. The Aerospace Corporation’s Debris Analysis Response Tool (DART) is a predictive model that can estimate the debris created from ASAT intercepts and other breakup events. The tool utilizes the target mass, pro- jectile mass, and relative velocity to statistically model debris created from a frag- mentation event. This report forensically evaluates India’s claim that the debris cloud will disperse and reenter in the weeks following the intercept. INTRODUCTION This paper will undertake a forensic reconstruction of the Indian ASAT demonstration which occurred on 27 March 2019. To provide the reader with a sense of the type of data products and after-action reports available during real-world operations using the DART software, it is here noted that the majority of the content in this report was generated within the initial hours following the intercept event. This software has been developed by The Aerospace Corporation and refined over the past decade to provide a rapid assessment of risk for key decision makers in the govern- ment. APPROACH AND TOOLS The Debris Analysis Response Tool (DART) is a predictive model that can estimate the debris created from ASAT intercepts and other breakup events. The tool utilizes the target mass, projectile mass, and relative velocity to statistically model the initial debris cloud created from a fragmenta- tion event using software called IMPACT. Once the breakup event’s initial conditions are deter- mined, the software will return a statistically representative ensemble of debris particles that accu- rately reflect what is expected to be seen in the real-world debris clouds (both target and projectile clouds) at the moment of intercept. The IMPACT model1, 2 has over 20 years of heritage and is informed by: 1. first principle physics (conservation of mass, momentum, energy, etc.), 2. ground testing and forensic reconstruction of hypervelocity impact tests, 3. real-world, post-event reconstruction of several historic breakups (collisions, explo- sions, ASAT intercepts, etc.). * Senior Member of the Technical Staff, The Aerospace Corporation, 14301 Sullyfield Circle, Unit C., Chantilly VA 20151-1622. 1 DART then propagates these debris clouds into the future and quantifies the probability of de- bris objects colliding with other satellites. Propagation is accomplished via a semi-analytic method that accounts for some higher order gravity terms as well as atmospheric drag. This risk data is then rapidly aggregated into various charts and can be plotted over time along with statistics de- scribing the debris cloud’s evolution. This tool can be used to determine debris risk3 within hours of a fragmentation event4 – well before most trackable debris objects are tracked by surveillance sensors and can be actively avoided. Furthermore, the software accounts for debris objects that are too small to ever be tracked yet are still large enough to be considered lethal. DART can also identify satellites that may fly through the “wrong place at the wrong time” (otherwise known as the debris cloud’s pinch-point) and offer advanced warning to these spacecraft operators as well as potential event attribution should a spacecraft suddenly fail after flying through a dense portion of the debris clouds. DART has been cross-compared with two other government tools5 and was found to agree quite well with them as any identified differences were proven to be statistically insignificant given the scenarios evaluated. Furthermore, DART can be used in several different applications including: • evaluations of real-world events on operationally-relevant timelines (hours to deliver product) which is the focus of this paper, • “what-if”, wargame, and pre-event scenario evaluation if salient input parameters can be accurately estimated, • long-term studies that can influence acquisition, strategy, and policy decisions. GATHERING DATA FOR INITIAL CONDITIONS On 27 March 2019 India announced the successful execution of a DA-ASAT demonstration6. G. Satheesh Reddy, Chief of India’s Defense Research and Development Organization (DRDO), identified the target as Microsat-R (SATCAT ID 43947, International Designator 2019-006A). Mi- crosat-R is reported to have a mass of 740 - 750 kg. Reddy reports that the Kinetic Kill Vehicle (KKV) hit its target to within 10 cm of accuracy. Sources7, 8 report that this operation, codenamed “Mission Shakti”, launched from Abdul Kalam Island sometime on March 27th. Space-Track.org TLEs of 43947 were used in Aerospace’s Satellite Orbital Analysis Program (SOAP) to identify likely launch times. Using SOAP, the analyst determined that Microsat-R flew directly over Abdul Kalam Island twice each day: Once at 05:42:46 UTC under sun-illumination conditions (mid-day local time) and once at 18:17:16 UTC under eclipse conditions. The first opportunity (05:42 UTC) seems to be the more likely candidate due to the mid-day local time illumination conditions. Fur- thermore, Microsat-R passes directly overhead rather than being offset to the west by 400 km as can be seen in Figure 1. Now that a likely intercept opportunity has been identified it is necessary to determine the pre- cise intercept time as well as the approximate trajectory of the KKV. Lt. General David Thompson indicated in congressional testimony9 that the ASAT launch occurred at 05:39 UTC. There are no sources indicating the precise intercept time; however, Prime Minister Narendra Modi stated10 that the interceptor’s flight time was 3 minutes in duration which corresponds to an impact epoch esti- mate of 2019 March 27 at 05:42 UTC and an altitude of 281.7 km. This intercept epoch seems reasonable since it keeps the impact point over the ocean (note that 46 seconds later Microsat-R is over land). An impact over the ocean would require the ASAT to be launched over the ocean which is safer than launching it over land (in case of vehicle failure). An ocean impact also aligns well with the Indian Notice To Airmen (NOTAM) 11 closing airspace over the ocean and preventing aircraft from colliding with potential sub-orbital KKV debris. 2 Figure 1. Passes on: 2019 March 27 05:42:46 UTC (left) and 2019 March 27 18:17:16 UTC (right). Since the position of Microsat-R at the time of impact is known (from the propagated TLE), the launch site position is known, and the time-of-flight is known, the trajectory of the KKV can be modeled using a Lambert solver that calculates a ballistic trajectory using a single ΔV applied at the launch site. Although this does not precisely model the boost phase, the trajectory is a reason- able approximation of reality and enables rapid assessment of such intercept events. The trajectory of the interceptor, along with the outline of the NOTAM region, is shown in Figure 2. Figure 2. Moments Before Intercept Occurring at 05:42 UTC and 281.7 km Altitude. The mass of the Indian KKV is unknown but can be estimated via photographs taken from an official video12 released by the government of India which documented Mission Shakti. Based on the photographic evidence (see Figure 3), 100 kg was used in this analysis as a reasonable estimate for the mass of the KKV. 3 Figure 3. Several Images Taken from a Government of India Video Showing the Booster and KKV Based on the described initial conditions, SOAP was used to determine several salient factors of the KKV intercept. The intercept occurred at an altitude of 281.7 km with a relative speed of 9.75 km/s. This high relative velocity led to a large amount of debris created due to the hyperveloc- ity and catastrophic nature of this collision. It is nearly certain that the KKV approached Microsat- R from below its inertial velocity vector rather than head-on. In this analysis the angle of the inter- cept is 23o below the velocity vector which is representative of a lower bound due to the Lambert modeling technique. The study was repeated with an angle of 45o (representative of a likely upper- bound) but did not alter the relative velocity. The resulting analysis products, like those presented below, did not change in a statistically meaningful way thereby illustrating the relative insensitivity to approach angle. What matters the most is relative velocity and mass due to the nearly isentropic spreading of debris that is so characteristic of hypervelocity collisions. RESULTS At the moment of intercept the DART/IMPACT model predicts the creation of 297,000 debris fragments larger than 1 cm. This cut-off size is generally considered the threshold for guaranteed lethality should such a particle collide with another satellite. Results are summarized in Figure 4. The KKV produces about 42,000 fragments larger than 1 cm while Microsat-R produces 255,000 fragments. Of course, most of those fragments are very small and, therefore, are untrackable. The DART analysis predicts that 391 particles should be trackable immediately after the event (larger than about 10 cm) although not every particle is likely to be cataloged since it historically has taken many days or weeks to track and catalog new space objects but by then several of these objects will have reentered. 4 Figure 4. Fragment Distribution Plot. Figures 5 and 6 illustrate the predicted spread of this debris cloud in a Gabbard plot that shows one object reaching an apogee of around 6,800 km as modeled by DART. Figure 5 displays all DART objects larger than 1 cm while Figure 6 only displays objects larger than 10 cm to make a fair comparison with real objects that have been tracked, cataloged, and added to the figures as well (taken from the 10 April 2019 catalog).