Evaluation of the 27 March 2019 Indian Asat Demonstration

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, projectile mass, and relative velocity to statistically model debris created from a fragmentation 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 government.

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 fragmentation event using software called IMPACT. Once the breakup event’s initial conditions are determined, the software will return a statistically representative ensemble of debris particles that accurately 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 debris 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 precise 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 estimate 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 reasonable 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.

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 hypervelocity 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 intercept 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.

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). Notice the good match between tracked and modeled particles as only two modeled particles exist without a tracked counterpart nearby. Of course, such fragments could have existed for a brief period before reentering and would therefore lack a corre- sponding catalog entry. It is also important to note that some tracked particles fell outside of the DART predicted envelope but always have a much lower period which is indicative of a rapidly reentering object. Finally, note that all objects (DART or tracked) have perigees that lie below the collision altitude which is exactly what is expected if you consider the fact that each fragment is created by adding a single ΔV applied at intercept. The orbital evolution of the debris objects is of extreme importance when quantifying the threat this cloud poses to the space environment. It is well known that these types of hypervelocity collisions manifest themselves as a nearly isentropic explosion of fragments when viewed from the target’s or projectile’s own reference frame. This can be seen in the results as the center-of-mass of Microsat-R’s debris cloud initially has a 90 m/s velocity relative to the un-intercepted parent body. That represents a momentum change of only 1% compared with the total orbital momentum of Microsat-R. Essentially the objects involved in the collision pass through one another without substantially altering their post-collision trajectories (albeit in several small pieces rather than just one). The defining characteristic of this ASAT demonstration lies in the claim that the debris is very short-lived. The primary driver behind this attribute is the relatively low intercept altitude of 282

5 km. Figure 7 and Table 1 illustrates this decay over time. Notice that about 70% of the initial debris that is created is sub-orbital and is removed by the atmosphere immediately. All debris from the KKV is sub-orbital, since the KKV itself was sub-orbital, and lands within the NOTAM region. About half of the Microsat-R debris loses orbital energy from the impact while the remaining half gains energy. In this case, the intercept altitude is so low that most objects which lose orbital energy also become sub-orbital. The result is that after 30 days only 1% of the original debris remains in orbit with a further reduction to 0.3% after 60 days. Most of the surviving debris will tend to be larger as small objects have larger area-to-mass ratios (hence larger drag perturbations and corre- spondingly shorter lifetimes) than large ones. This seems to support India’s claim of a 45-day debris cloud lifetime.

Figure 5. Gabbard Plot Shown with Predictive DART as well as Actually Tracked Data (>1 cm).

Figure 6. Gabbard Plot Shown with Predictive DART as well as Actually Tracked Data (> 10 cm).

Figure 7. 60 Day Decay Plot.

Table 1. Particle Count and Mass Over Time (Particles > 1 cm). Time (Days) Remaining Particles Remaining Mass 0 31.6% 26.6% 1 24.4% 21.6% 2 18.4% 16.8% 3 14.9% 14.5% 10 5.3% 6.8% 20 2.0% 3.2% 30 1.0% 2.0% 40 0.6% 1.7% 50 0.4% 1.4% 60 0.3% 0.4%

The debris cloud can also be analyzed from the perspective of spatial density. Figure 8 shows the spatial density (via altitude bins) of the debris cloud as a function of time. The log of the spatial density (particles/km3) is plotted on a color scale and, in the case of Microsat-R, can be seen with a peak density near the breakup altitude and quickly decaying over time as it gently fades to pre- existing background levels. Figure 9 compares the Microsat-R intercept to two other historical intercepts: (1) the 2007 Chinese intercept of the FY-1C satellite and (2) the 2008 U.S. intercept of a U.S. satellite. Notice that the Indian demonstration is extremely similar to the U.S. action in 2008 with very short lived debris clouds for both events due to their low intercept altitudes which were much less than 300 km. In contrast, the Chinese intercept of FY-1C in 2007 occurred at an intercept altitude of 856 km and therefore created debris likely remaining in orbit for decades. A summary of the historical DA-ASAT intercepts can be found in Table 2. Figures 10 and 11 illustrate the decay of tracked debris fragments associated with four historical DA-ASAT intercepts. Notice how the Solwind intercept of 1985, at an altitude of 555 km, required nearly 20 years for the last tracked object to reenter compared with the U.S. satellite intercept of 2008 which took around a year and a half to do the same. It is expected that the debris cloud associated with Microsat-R will have a similar lifespan.

Figure 8. Debris Spatial Density Plot Over Time.

Figure 9. Debris Spatial Density of Three Historic DA-ASAT Intercepts (Same Scales).

Table 2. A Summary of All Four Historical DA-ASAT Intercepts.

Figure 10. Tracked Debris Cloud Objects Decaying Over Time for Four Historical Intercepts.

Figure 11. Tracked Debris Cloud Objects Decaying Over Time for Four Historical Intercepts.

The DART software evaluated the collision risk that the modeled debris from Microsat-R posed to other satellites. The resulting risk was then scaled by the pre-existing background risk using the following formula: Absolute Risk + Background Risk 푅푒푙푎푡푖푣푒 푅푖푠푘 = Background Risk Using this formula, zero risk from the cloud corresponds to a relative risk value of one. For risk to be considered statistically significant (given the evaluation method) a risk of 10 times the background or more is generally required. For the case of Microsat-R, no satellites experienced risk that rose to this threshold. The International Space Station, for example, experienced a peak risk, on March 28th, of 1.23 times the pre-existing background (or 23% more than usual). This is not a statistically significant increase. The other satellites in LEO as well show similar results. Figures 12 and 13 record the relative risk over a two-week period for select satellites and illustrate the evolution in risk to some of the most affected satellites in LEO. Overall, the mild increase in risk faded to pre-event background levels within a matter of days. Figure 14 shows the highest risk experienced by any satellite over the first six days post-intercept. Note the highest risk experienced by any satellite was 1.7 times the background risk which is not considered to be statistically significant.

Figure 12. Risk to Iridium Satellites.

Figure 13. Risk to Select Satellites.

Figure 14. Daily Tables Ranked by Highest Risk to LEO Satellites (Six Total Days).

The debris cloud from Microsat-R can be visualized using a method13 that accounts for the density of the debris particles and the way in which that density evolves over time as the debris cloud grows, disperses, and reenters. This is accomplished by identifying fragments that constitute the 95th percentile of the relative velocity distribution (relative to the parent body, Microsat-R) at the moment of intercept. These particles then can be used to define the surface of a three-dimensional torus which evolves over time as the particles are propagated. Note that all other particles, having slower spreading speeds by definition, will (for all practical purposes) be contained within the torus. In this way the entire debris cloud can be visualized by the evolving surface of a torus over time. Figures 15 – 21 illustrate the evolution of the Microsat-R debris cloud over the first week of its existence. As with the spatial density plots of Figures 8 and 9, the torus is colored using a log scale of spatial density with red being the highest density and blue being the lowest. Notice that a significant portion of the debris cloud is clipped by the atmosphere causing a large amount of the debris objects to reenter as predicted. Also note the existence of the “pinch point” which is the location in inertial space where the intercept occurred and which all fragments must return to (although not simultaneously since they are on different orbits). This represents the portion of the cloud with the highest spatial density and, therefore, the highest risk to other satellites.

Figure 15. Debris Cloud Evolution (T + 5 min).

Figure 16. Debris Cloud Evolution (T + 0.5 Rev).

Figure 17. Debris Cloud Evolution (T + 1 Rev).

Figure 18. Debris Cloud Evolution (T + 1 Day).

Figure 19. Debris Cloud Evolution (T + 2 Days).

Figure 20. Debris Cloud Evolution (T + 3 Days).

Figure 21. Debris Cloud Evolution (T + 6 Days).

It is interesting to note that the first few moments of this evolving debris cloud were captured by Indian cameras on the ground. Figure 22 illustrates the expanding debris cloud during this time. The figure also shows the final frame of a video12 feed from the Imaging Infrared Camera used for terminal guidance on the KKV giving high confidence of a direct hit (which is consistent with this DART analysis) rather than a glancing blow.

Figure 22. Microsat-R Moments Before (Left) and After (Right) The Intercept.12 he final consideration to be evaluated in this analysis was the number of conjunctions created by the debris cloud of Microsat-R. The 10 April 2019 catalog was used to screen all the active LEO satellites against the cataloged debris from Microsat-R. Results are plotted in Figure 23 for a miss distance of up to 15 km. Out of the nearly 2,000 active satellites, approximately half that number experienced a conjunction within that threshold during the month following the intercept event.

17 Overall, more than 3,000 conjunctions were identified with a few of those (about a dozen or so) resulting in what may be reportable14 conjunction warnings (less than 1 km).

Figure 23. Number of Conjunctions Between U.S. Cataloged Debris and Active Satellites.

SUMMARY On March 27, 2019 near 05:42 UTC India intercepted Microsat-R (SATCAT ID 43947) with an indigenous ASAT. India claims the KKV hit Microsat-R and destroyed it in a responsible manner that limited the debris cloud’s lifetime to one or two months. Due to the low altitude of the intercept (282 km) India’s claim seems to be verified as less than 1% of the estimated initial 397,000 debris particles greater than 1 cm in size are predicted to remain in orbit for a month or two post- intercept. This intercept was similar in nature to the 2008 intercept of a U.S. satellite including the debris lifetime. In stark contrast is the 2007 FY-1C intercept by China which was conducted much higher and resulted in debris lifetimes of several decades or more. Finally, no satellites saw a statistically significant increase in collision risk as a result of this Indian ASAT demonstration.

AKNOLWLEGEMENTS The author would like to acknowledge the contributions of his Aerospace colleagues. Roger Thompson cross-checked much of the analysis work presented here with his own analysis work using the DART software. Roger Thompson, Brian Hansen, and Rob Cumby reviewed this paper and provided constructive criticism to enhance its quality. Britany Chamberlain and Michael Rose wrote code that contributed to Figures 10 and 11. This paper was reviewed and approved for public release by The Aerospace Corporation: OTR-2019-00884.

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