abbreviated terms

CCSDSConsultative Committee for Space Data Systems
CDMConjunction Data Message
SSASpace Situational Awareness
SSRSpace Sustainability Rating
SSTSpace Surveillance and Tracking
TLETwo-Line Elements

OVERVIEW

This section covers the essential capabilities that satellite operators should have, to improve their ability to identify, respond to, and mitigate collisions. The methodology groups the capabilities in four categories, with a number of items of increasing value in each category.

1. Orbital State Knowledge

Rationale: Cooperative tracking often results in smaller covariances, as do more frequent tracking and improved information about planned satellite manoeuvres (e.g. by characterising the manoeuvre uncertainties).

The SSR gives additional credit for better orbit determination, more frequently updated orbit determinations, and better characterized/validated covariance estimation. This could help spur better orbit determination capabilities, especially for small satellites that might otherwise lack it. In the absence of an industry-wide standard for covariance estimation, knowing you have well-characterized the realism of your covariance information helps other operators determine whether to trust provided covariance estimates.

The accuracy which can be achieved on the orbital state knowledge, in any spatial direction, is orbit-regime dependent and can be influenced by the chosen technologies. A top-level distinction between coarse and accurate is to be made, which can be assessed by the SSR issuer.

 

2. Collision Avoidance: Availability to Coordinate

Rationale: Operators should be credited for maintaining service availability to coordinate with other operators for collision avoidance and being reachable for collision avoidance purposes with high availability.

3. Collision Avoidance: Capability to Coordinate

Rationale: Operators should be credited for maintaining staff with expertise to meaningfully resolve the potential event, namely:

a) Ability to accept and interpret common data formats including conjunction data messages (CDMs) and other Consultative Committee for Space Data Systems (CCSDS) standards;

b) Ability to review various sources of SSA information and determine the level of risk posed by a conjunction and whether a manoeuvre is indicated, not-indicated, or if further information is needed;

c) Ability to develop manoeuvre plans to mitigate a conjunction, screen manoeuvre plans from other operators for safety; and ability to task new non-routine manoeuvres for your satellites and confirm execution. Documented procedures help prevent human and technical errors during critical safety of flight operations.

4. Collision Avoidance: Manoeuvre capability

Rationale: Operators should be credited for implementing capabilities to avoid collisions. A relatively low thrust level implemented within a few revolutions can greatly enhance spaceflight safety and will be rewarded as part of the rating.

 

Table 1: Scoring Rubric for Collision Avoidance Capability

Orbital State Knowledge (during normal operations) Rely on a third party public SSA provider for state information (e.g. space-track.org TLE) Operator maintained orbital position state knowledge of object [*] Maintain orbital state knowledge of object to < 10 km in any direction

Update orbit determination for the operated satellite when a manoeuvre or other event induces a change to its orbit that would cause the operator’s state estimation to be worse than the required orbital state knowledge

Characterize/validate covariance of your orbit determination
Maintain orbital state knowledge of object to within < 1 km in any direction

Update orbit determination for the operated satellite when a manoeuvre or other event induces a change to its orbit that would cause the operator’s state estimation to be worse than the required orbital state knowledge

Characterize/validate covariance of your orbit determination
Collision Avoidance: Availability to Coordinate Not able to coordinate Able to coordinate in response to emergencies (but not necessarily on a routine basis) Able to coordinate during set hours per day Has a system for routine conjunction assessment and capability to respond to concerns 24 hours per day via human or computer system capable of supporting near-immediate coordination and reaction for urgent issues
Collision Avoidance: Capability to Coordinate Operator has no dedicated process for conjunction screening, assessment, or mitigation

The operator may be unable to or chose not to ever manoeuvre in response to conjunctions
Has the capability to be contacted in case of close approach or another high-risk event

Operator regularly screens orbits and planned manoeuvres against public catalogues and/or information from SSA sharing organizations and/or third-party SSA providers
Operator is capable of interpreting conjunction data messages and other common formats, to determine risk and generate/screen mitigating manoeuvres

Operator has a system for automated routine conjunction assessment
Has documented procedures for collision screening, assessment, and mitigation

Regularly screens operational spacecraft and planned manoeuvres against SSA sharing organization catalogue
Collision avoidance: manoeuvre capability No maneuver capabilities Any maneuver capabilities (including differential drag) Reaction (at least ∆v=1 cm/s) within 6 orbital revolutions Reaction (at least ∆v=1 cm/s) within 1 orbital revolution
(BONUS)

Maintaining orbital state knowledge after the end of normal operations
Maintain orbital state knowledge until spacecraft is placed into a graveyard orbit or is disposed of through atmospheric re-entry Maintain orbital state knowledge to 10 km until spacecraft is placed into a graveyard orbit or is disposed of through atmospheric re-entry Maintain orbital state knowledge to 1 km until spacecraft is placed into a graveyard orbit or is disposed of through atmospheric re-entry

Scoring Guidance: Entities can receive credit for any box where they satisfy all criteria contained in the box. If an operator is able to fulfil multiple boxes in a single row, those point values are added. During the scoring process, the total number of points earned by the entity are divided by the total possible points. The normalized point total is an input to the full SSR calculation.