What is space domain awareness (SDA)? It’s the ability to know what’s going on in space, and how it affects us on Earth. SDA involves finding out and understanding everything that’s in space, whether it’s made by humans or nature. SDA helps us to keep our space activities safe and secure, and to protect our planet from any harm.
Space Domain Awareness
Space Domain Awareness (SDA) encompasses the systematic assessment of various aspects related to space operations, including orbital dynamics, satellite capabilities, space traffic, and potential threats. With space becoming congested and potentially hazardous, SDA plays a vital role in maintaining a safe and secure environment for space operations. Understanding and monitoring this domain is essential for various stakeholders, including government agencies, satellite operators, and commercial space entities.
A critical aspect of SDA is the identification and assessment of potential threats in space. As space becomes more accessible, the risk of intentional attacks on satellites or other critical space assets increases. SDA systems analyse various parameters and behaviours to identify potential threats, such as anti-satellite weapons or hostile manoeuvres by other nations’ satellites. Early detection and analysis of these threats allow for timely response and countermeasures.
Observation of adversary’s activities in space includes undeclared satellite launches, parasitic satellites, Intentional manoeuvres, space robotic activities, detection of adversary’s counter space activities etc. SDA include the intelligence of the adversary’s satellite design, payload and employment, monitoring the adversary’s missile launches to augment its ballistic missile defence warning system.
This also includes activities to identify orbiting space objects, assess their hazard, establish ownership and predict the possible intention and usage by an adversary. Communication intelligence (COMINT) and electronic intelligence (ELINT) of adversary’s space assets and their geo- location are also a part of SDA.
In essence, SDA is an expansion of the scope of SSA to address threats arising from ground-based elements that may potentially affect space activities. For SDA, the knowledge of the intent of a space actor is the key. To achieve this objective, SSA data is collated with additional intelligence to trace the origin of a given activity and attribute its intent (whether friendly or hostile) to aid further decision- making. Therefore, SDA is of paramount importance to ensure service availability of space assets during warfare.
Space Traffic Management
The rapid expansion of satellite constellations, and burgeoning commercial space endeavours have ushered in an era where the management of space traffic has become Imperative. Space Traffic Management (STM) stems from a requirement of regulatory procedures to ensure risk free coordination and planning of space operations in a safe manner.
Definition about STM
AIAA International Space Cooperation Workshop 2001 led to the establishment of the STM working group at the International Academy of Astronautics (IAA) for activities intended to prevent damage in the near term (such as collision avoidance and coordination of re-entry), as well as actions that must be taken to prevent long-term potential for future damage”. The first comprehensive study about STM is due to the Cosmic Study on Space Traffic Management 2006. It defines STM as “the set of technical and regulatory provisions for promoting safe access into outer space, operations in outer space and return from outer space to Earth, free from physical or radio-frequency interference”.
Legal Subcommittee of UNCOPUOS 2016 defined STM as “development and implementation of a set of technical and regulatory provisions for promoting safe access to and from outer space, and for maintaining secure operations in space, free from physical or radiofrequency interference”, which is concurrent to the definition of STM provided by IAA in 2006. As per Space Policy Directive-3(SPD-3) US National Space Traffic Management Policy, 21 June 2018, “Space Traffic Management shall mean planning, coordination, and on-orbit synchronization of activities to enhance the safety, stability, and sustainability of operations in the space environment.”
All these definitions emphasise on the need for coordination amongst space actors. STM focuses on evolving standards of rules and regulations during launch, on-orbit operations and re-entry phases that are to be adopted internationally. It primarily deals with safety and sustainability of outer space activities, the scope spans across national, international, civil and military space activities. STM involves “best practices, technical guidelines, safety standards, and behavioural norms” for
a) Pre-launch risk assessment
b) On-orbit collision service
c) Re-entry risk assessment
d) Minimising harmful interference
International coordination and cooperation are crucial for STM. SSA and STM have multiple overlapping elements with the same end goal which is the long-term sustainability of outer space activities. STM demands advanced capabilities in tracking and monitoring, data sharing and related services. Therefore, STM functions are heavily dependent on SSA capability, this makes STM a component of SSA.
The main STM goals are enumerated below: • Adopt guideline and standards on space debris mitigation
* Enhance SSA capabilities by adopting newer tools and techniques, including modelling of small debris environment
* Improve interoperability of SSA data and information to enable greater data sharing
* Evolve regulatory policies for orbital operations without interference
* Improve registration practices to keep track of objects launched in space and establish liability for any damages
The Outer Space Treaty (OST), formally known as the “Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies” laid the foundation for responsible behaviour in space at an era when only a few countries (States) dominated the space arena. As per OST, outer space is a province of humankind to be explored and utilised for peaceful purposes. It prohibits the weaponisation of outer space, upholds freedom of utilisation with due regard to the interest of the other States Parties, and discourages actions that may result in harmful interference with the activities of other States.
States are liable for damage caused by their space objects, whether in outer space or on Earth which provide impetus to avoid on- orbit break-ups and collisions. In particular, OST emphasises international collaboration and consultation for any dispute resolution. While the fundamental principles enshrined in the OST remain relevant, there is an urgent need to formulate regulations that address the current scenario in the space domain.
The International Telecommunication Union (ITU), the UN agency for information and communication technologies, has been playing a significant role in STM. It is responsible for the efficient allocation of specific radio-frequency bands to satellites which ensures the avoidance of radio frequency interference with the already existing, neighbouring satellites. It also coordinates the allocation of specific orbital slots for GEO satellites, again to avoid potential collisions or radio- frequency interference.
Inter-Agency Space Debris Coordination Committee also has played an important role by formulating guidelines that preserve the safety and sustainability of outer space. Certain provisions within these guidelines directly influence the space environment, such as preventing on-orbit break-ups and limiting the release of mission related debris which help reduce collision hazards in space. IADC also recommends specific strategies for post mission disposal that ensure that the disposal orbits are well outside the highly utilised orbital zones.
There are initiatives by spacecraft operators towards STM. Space Data Association (SDA) is a not- for-profit international consortium of several commercial and government-owned satellite operators (Intelsat, Eutelsat, Inmarsat, Arabsat, Iridium, OrbComm etc.) established as a legal entity in 2009. Several governmental space agencies such as NASA, NOAA, DLR and Eumetsat are also members. It enables controlled, reliable sharing of operator-to-operator data of civilian satellites to improve space situational awareness, and offers services for collision avoidance and radio frequency (RF) interference mitigation.
Current Scenario in Space
The scenario for space traffic is quite different from air and marine traffic. For aviation, there exists the International Civil Aviation Organization, a UN specialised agency, which supervises the relevant standards and practices and also decides the protocols for air accident investigation, International Maritime Law is maintained by the International Maritime Organization. In contrast, there is no such organisation responsible for formulating and implementing a streamlined, globally acceptable set of rules for space traffic. Although STM has been a regular topic in the legal subcommittee of the UN, no consensus exists between the member States. The prevailing issue with STM is more of a governance problem than a technical one.
At present STM is an ad hoc, informal process followed among space actors based on their mutual understanding. Such a process is unsustainable to cope with the steep influx of space traffic that would deteriorate space congestion, especially in the LEO. A lack of effective STM will lead to operators having to conduct collision avoidance manoeuvres based on an overly conservative assessment of the situation, which will incur additional operational penalties in terms of fuel and service disruptions, reducing the return on investment for the space assets.
Difference between SSA and STM
SSA involves generating information about the entire space environment, including positioning of space objects, space weather, and radio frequency interference, it covers a much wider spectrum of
activities. Here, the focus is not just limited to gathering knowledge of the space environment but also involves informed decision making based on the current knowledge. While STM is a subset of SSA, its focus is on collaboration, coordination, regulation towards promoting responsible behaviour in space.
SSA and STM Challenges
Direct measurement data on small debris (mm sized) is needed to support the development and implementation of cost-effective protective measures for the safe operations of future missions. The recent addition of the Space Fence radar extends the Space Surveillance Network of the US to the degree of about 2 cm. NASA uses additional radars including Goldstone and HUSIR (Haystack Ultra- wideband Satellite Imaging. Radar) that can track up to 3 mm-sized objects. Data from the sub millimetre sized debris comes from the inspection of hardware returned for servicing from space.
Despite this, there is a critical data gap between 600 to 900 km altitude for mm-sized space debris. This is because more than 1000s of spacecraft operate in this range and mm-sized space debris represents the highest mission-ending risk to those spacecraft in this regime. The lack of direct observation creates a concerning data gap.
The guidelines for space debris mitigation laid down by the UN/IADC are followed by space-faring nations. They are translated into engineering practices by all major space agencies, tailored to suit national space policies and documented as mitigation requirements or standard practices. Some of these regulations are qualitative and very high level. Guidelines have to be specific, quantitative, and measurable. The main issue is the lack of compliance with the mitigation guidelines and adherence to the best practices leading to the present debris situation.
Remediation efforts for long-term space debris include active debris removal. On-orbit servicing is another option as it is easier and cheaper to upkeep the orbiting upper state or spacecraft at the end of mission operations with sufficient fuel than trying to remove them later with another mission as it is very expensive and difficult. Alternative technologies need to be explored to remediate the long- term space debris problem. Furthermore, the regions identified for the debris removal is dominated by debris belonging to other countries and hence the ownership issues need to be addressed while performing an ADR.
Orbit determination, orbit analysis, orbit propagation techniques, data formats and exchanges, data aggregation, sensor calibration, tracking thousands of objects for long periods, data integration, data security and data verification are some of the prominent challenges in implementing SSA. This may be due to earth orientation, insufficient metrics, timing-based errors, uncalibrated sensors, unknown space weather, unmodelled manoeuvres, sensor light conditions, inadequate quality control, under- sampled observations, unrealistic covariance, low thrust manoeuvring etc., Hence the accuracy of data used for SSA becomes a challenge.
The domain is inherently global, and objects in space transcend national boundaries. Therefore, coordination and information sharing are crucial to ensure the safety of all space assets and to mitigate the risk of collisions. International cooperation in SSA enhances transparency and trust among nations. By openly sharing data on space activities, including satellite launches, manoeuvres, and potential threats, States can demonstrate their commitment to responsible and peaceful use of outer space. Sharing of data among the space-faring nations, sharing of sensor networks across nations, and establishing newer sensor facilities are ways to effective SSA, SDA and STM.
The emergence of new space players, such as private companies and non-state actors, adds complexity to the SSA landscape. To meet these challenges, investments in research and development of advanced sensors, data processing algorithms, usage of machine learning and artificial intelligence will be crucial.
Over the years ISRO has developed substantial capabilities for SSA related analyses and have made significant contribution to protect operational Indian assets and mitigate space debris. ISRO’s SSA activities are currently focussed on
* Establishing a robust, indigenous observational capability of space objects, including space debris, through a network of tracking facilities
* Evolving a reliable, end-to-end operational mechanism to process tracking observations
* Continual assessments of space situations to enable safe mission operations
* Dissemination of SSA information in a timely manner
* Capacity building for space weather prediction, natural threat detection and monitoring
* Active participation in global efforts of SSA information exchange by sharing observational data on Resident Space Objects (RSO)
ISRO follows UN COPUOS/IADC guidelines for space debris mitigation. The implemented measures include passivation of Launch Vehicles upper stages, re-orbiting of GEO satellites into higher orbits and passivation at end-of-life, post-mission disposal for LEO missions by de-orbiting LV upper stages, launch COLA collision avoidance, the most recent milestones include the controlled re-entry of MegaTropiques-1 satellite over the South Pacific Ocean and de-orbiting of PSLV-C56 upper stage to 300 km circular orbit after satellite injection. As a further initiative towards the preservation of the space environment for the future, ISRO has also formulated India’s requirements for space debris mitigation and management.
Setting up of the ISRO System for Safe Stable and Sustainable Space Operations Management (IS40M) marks another major milestone, for the establishment of dedicated observational facilities (RADARS, Telescopes, space-based platforms) to obtain more accurate orbital information of space objects, extensive coordination with national and international bodies to avoid on-orbit collisions, collaboration with academia and research institutes for the assessment of the orbital space debris environment, engagement with emerging Indian space sectors to raise the awareness on the importance of space debris mitigation for long-term sustainability of space activity.
Space assets are vital for national security, including communication, navigation, surveillance, and more. Space Situational Awareness plays a key role in protecting these assets by identifying potential threats and anomalies in space. Space Traffic Management is an evolving discipline that has gained paramount importance due to the growing congestion in outer space. It is essential for protecting valuable space assets, ensuring the safety of astronauts, and preserving the sustainability of space for future generations.
As humanity’s activities in space continue to expand, SSA and STM will gain further importance in addressing the associated challenges and opportunities. Raising awareness about the importance of SSA and STM is one of the most important steps to foster support for responsible space activities and policies. Through international cooperation, innovative technologies, and responsible practices, we can overcome the current challenges and continue to explore and utilise the vast potential of outer space for the benefit of humankind.