Defending Space Assets

Defending Space Assets


AThe prospect of Earth being ruled from space is no longer a science fiction. Today, technology exists to weaponise space. In the article, the writer proposes space based mechanisms for monitoring and depriving an enemy the advantage of space while at the same time, making provisions for protection and survivability of one’s own space assets.

In the present day scenario, most of the operations either in civil or military space, are being carried out through the assistance of satellites. These include monitoring of rivers, forests, agriculture, etc., or navigational or communication applications. This strategic importance of satellites has made them vulnerable to enemy attacks in recent times. These activities are fundamentally intended to deny the advantage of space to an enemy. Thus, there is a strong need to study the vulnerabilities and threat perceptions of space assets and take corrective actions to prevent an enemy attack.

On February 20, 2008, the US Navy destroyed USA-193 by using a SM-3 ABM acting as an anti-satellite weapon. USA-193 was an American spy satellite which was decaying from orbit at a rate of 1,640 feet (500 m) per day. Chinese ASAT activities such as destroying its weather satellite on January 11, 2007, and similar other tests need to be noted for protection of space assets. The use of high altitude nuclear explosions to destroy satellites was considered after noting the damaging effects of the electromagnetic pulse (EMP) caused by the explosions on electronic equipment. Another area of research was directed into energy weapons using conventional lasers or masers. Therefore, ASAT weapons are classified as follows which can be perceived as a threat to LEO and GEO satellites.

  • ASAT missiles (ground/ air launched or with nuclear/ nonnuclear/ kinetic warhead)
  • EMP based ASAT weapons (nuclear/ non-nuclear)
  • Laser/ Directed Energy Weapons Systems (DEWs)
  • Modification of launch vehicles as ASAT missiles

The eminent threat perception to space assets can be classified as follows.

  • Threat to LEO satellites
  • Threat to GEO satellites
  • Threat from DEWs
  • Threat to ground stations

Threat to LEO Satellites

Any medium range ballistic missile, with a ground range of 500-2,500 km can be stated as direct-ascent ASATs posing a serious challenge to photographic intelligence (PHOTINT), electro-optical (EO), synthetic aperture radar (SAR), and electronic intelligence (ELINT) satellites that operate in low-earth orbit (LEO). It is also possible that direct-ascent ASATs could be armed with the electromagnetic pulse (nuclear or nonnuclear) warheads. Potential threat from DEWs such as ground based lasers and kinetic weapons cannot be ruled out.

Threat to GEO Satellites

At present, there is no readymade system which can threaten satellites in geostationary orbit, which is about 36,000 km from Earth’s surface. However, Intercontinental Ballistic Missile (ICBM) technology that may eventually be able to use a larger first-stage motor and an advanced guidance package can be redesigned to target satellites in GEO. Potential threat from DEWs placed on another GEO satellite based lasers and kinetic weapons cannot be ruled out.

Threat from Micro and Nano Satellites

Another potential threat is from micro and nano satellites which can also be used as ASAT weapons. Advances in miniaturisation and the proliferation of space technologies enable space faring nations to manufacture small, lightweight, inexpensive and highly capable systems that can perform a variety of missions. Included in this list of missions is counter-space operations, such as long-durationorbital inspection and intercept. Microsatellites can perform satellite inspection, imaging and other functions and could be adapted as weapons. Placed on an interception course and programmed to honein on a satellite, a microsatellite could fly alongside a target until commanded to disrupt, and then disable or destroy the target. It would be difficult to detect and defend against such an attack.

Futuristic Concepts and Proposed Methodologies

Analysis of fighter losses in 1960s indicated that at least 70 per cent of all losses were attributed to passive heat seeking (Infra Red) guided missiles. By visualising this threat, radar warning receivers were developed. They proved their effectiveness by early 1970s as they considerably improved the survival of aircraft against radar threats. The first air-to-air missiles appeared in 1950s. The invention and development of semiconductor technology allowed more compact missile designs and made it possible to develop IR Man Portable Air Defence Systems (MANPADS). Most aircraft that were shot down never knew that the missiles were approaching them. Over time, the performance and effectiveness of MANPADS have further increased due to advanced new seeker head technology. As per CSIS ‘Transactional Threats Update,’ Volume 1. No.10.2003 about 7,00,000 MANPADS have been produced, so far. At this point of time where satellite based technologies are controlling several aspects of economy, there is a need to apply these technologies for protection of space assets. For this, the following systems are required to be built into spacecrafts. They are –

  • Spacecraft radar and missile warning receivers
  • Spacecraft EW suite/ Electronic countermeasures
  • Ground based monitoring, support and control measures

Spacecraft Radar and Missile Warning Receivers (SRMWR)

Protecting spacecraft against threats depends mainly on reliable detection and warning system, and applying effective ECM for avoiding, evading and engaging threats. Two or three separate systems such as radar warning receiver, missile warning receiver and suitable countermeasures suite cannot be considered for spacecraft protection because of size, shape and operating cost of the craft. Also, payloads need to be reduced in size due to fitment of these protection systems onboard spacecraft. Hence, the following system and functional requirements are proposed for spacecraft radar, missile warning receiver and countermeasures suite:

  • There has to be a single integrated system for radar, missile warning and countermeasures, since this is meant for a spacecraft.
  • Designing SRMWR to provide timely detection and warning. This is a big challenge.
  • Missiles may not give any warning prior to their launch and may not rely on sensors such as IR, microwave or laser designator. Hence, SRMWR must be based on multi-sensor system.
  • Though the threats are based on long ranges, time available for detection, identification, ground based support and control actions is very less, therefore SRMWR must provide reliable (almost 100 per cent probability of warning) and timely warning to allow appropriate countermeasure responses.
  • SRMWR must allow very little margin for errors with very fast reaction time to effectively apply countermeasures.
  • SRMWR must have sufficiently very low false alarm rate even when illuminated by multiple threat sources from ground as well as space. This is more so since the ground support and decision makers will have to rely on it.
  • Very low false alarm rates and quick response time are inherently conflicting system requirements, hence it requires a balanced design and development approach to provide most successful space assets protection operation without compromising probability of threat warning. False alarms represent decision errors, which can only be reduced by gathering more data, which takes more time, inevitably reduces countermeasures deployment time. Due to this, it is suggested that space assets command and control operators would have to tolerate an increased false alarm rate.
  • Angle of attack (Azimuth and Elevation) is another critical and very important requirement for SRMWR, which need to provide sufficiently accurate initial pointing, so that suitable countermeasures can be deployed for acquisition and engagement of incoming missile threats successfully and in time.
  • Angle of attack data has to be so accurate for ground controllers to be able to decide the direction of dispensation of countermeasures, which is vital to avoiding a situation where the space based platform and the dispensation, both remain within the instantaneous field of view of incoming missile. This situation may not arise for space assets since their speed is very high.
  • Accuracy of angle of attack is further important for space based platform which requires orbital manoeuvre when dispensing countermeasures especially to increase the miss distance for better protection of space platform. This is very critical since space platform speed is very high which is likely to negate the separation of countermeasures ejection velocity.
  • An orbital manoeuvre towards incoming missile is more useful for increasing the angle between platform and the countermeasure, and especially important in cases where a threat is launched from the space based enemy platforms coming from rear side.
  • The SRMWR suite must also be fully automated as a single integrated package. This single suite must have the following capabilities:
    • To monitor and detect surveillance pulses which are intermittent.
    • To monitor and detect tracking pulses which will appear at short and regular fixed intervals.
    • To detect missile warning in which transmitted commands are sensed which will have variable duration pulses.
    • Proximity or radio fuse for countermeasures action.

All these functions have to be in a single package appropriately suitable to space assets which is to be designed and developed. With VVLSI chips, quad-core processing further miniaturisation and developments in digital technology, the development proposed in this paper is definitely feasible. The fitment of SRMWR in satellites requires the following:

  • Reduced payload
  • Increased onboard power consumption
  • Complexity commanding operations of the satellites payload
  • Onboard electronics systems maintenance responsibility
  • Necessity of launching additional satellites for same payload capacity. If micro satellites are launched to track the threats then the number of these threat monitoring satellites will increase and space will get congested
  • Enhanced ground support and complexity of operations
  • Increased costs

Physical Requirements of SRMWR

The SRMWR suite for space assets protection applications requires a special mention. In modern times, where there is a long wait and growing requirement for transponders and bandwidth, how can the lightweight spacecraft provide space and mass capacity for inbuilt protection equipment. The SRMWR should also not cause adverse orbital drag and must have minimal physical size and shape. The power consumption requirement must further be kept within the capacity of the spacecraft’s electrical system. To economise on the installation and integration costs and problems, suitable interfaces have to be designed to provide communication and co-existence with other onboard payloads of spacecraft.

Cost considerations

Initial design, development, installation, integration and trial cost will invariably be high along with direct and indirect cost implications. The system performance and availability of the protection suite is required for the entire life cycle of spacecraft. Indirect cost involves degradation of the spacecraft’s performance as a result of having the protection suite onboard and in turn impacts the operating cost of the spacecraft and its orbital life. In addition, quantity of such systems required will be very less, hence commercial viability for cost, quantity and performance factors have to be carefully assessed.


The proposed SRMWR is a single package for spacecraft defensive measures and must include countermeasures which can be classified as passive and active.

Passive Countermeasures
Passive countermeasures against radars, missiles and ASAT weapons attack include warning for hiding, evading, manoeuvre, and initiation of deceptive measures through electronic countermeasures and electro-optical countermeasures as well as combinations of these measures.

  • Hiding, for example, satellite miniaturisation and orbit selection
  • Manoeuvre from a ground station for evasion
  • Deception, for example, deploying lightweight decoys
  • Hardening, for example, use of shielding
  • Electronic countermeasures and electro-optical countermeasures, for example, use of shorter wavelengths and more highly directional antennas
  • Some of these countermeasures, for example, ‘hardening’ are truly passive, requiring no satellite activity for their effectiveness; while others like ‘evasion’ require satellite activity and hence attack warning, and are not truly passive, although they are non-destructive
  • The land infrastructure may be strengthened by adding more monitoring stations
  • Other passive countermeasures include deploying new generation satellites with high power signals thereby making jamming more difficult and deploying additional satellites for redundancy

Active Countermeasures
Passive countermeasures against ASAT attacks may be supplemented by active measures intended to deter ASAT attack or to defend satellites if deterrence should fail. Active measures can therefore be used for either defensive or retaliatory purposes. Defensive active measures are active countermeasures against ASAT attacks. Retaliatory active measures do not counter ASAT attacks but instead fulfil explicit or implied threats of retaliation which were intended to deter ASAT attacks. Active measures used for either purpose can be either nondestructive (for example, electronic countermeasures and electro-optical countermeasures) or destructive (for example, shoot back).

Constellation of Satellites

Another concept is to have two micro-satellites flying alongwith main satellite carrying SRMWR in fractioned functions, separately for radar-missile warning, and countermeasures suite which will have intercommunication facilities. This type of system reduces overall programme risk, provides budgetary and planning flexibility, speeds up initial deployment trials, involves no reduction in payload capacity, reduces load on onboard power requirement and offers greater survivability.

Diplomatic Measures
In addition to the military measures discussed above, diplomatic measures such as arms control initiatives and negotiation of ‘rules of the road’ for space operations could be useful responses to development of threatening ASAT capabilities.

We have seen in the recent and on-going conflicts world over that the importance of Military Space Operations has increased many folds due to the enabling capabilities they provide to a Commander. The proliferation in space operations dovetailed with defence space programme has given rise to operations such as Space Force Enhancement, Space Support, Space Control and Space Force Application.

It is expected that at least by 2020, all the space based assets which will be launched will possess capabilities for radar, missile warning and countermeasures actions for avoiding, evading and attacking. The concepts of SRMWR system configurations proposed in this paper are a step in the direction for achieving defensive capabilities for all spacecraft. But the technology has to be experimented with uitable trials for realisation.


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