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015 - Alert Criteria for Government

Purpose

This TEST design document proposes a means for UKSA staff to automatically and manually distribute re-entry and conjunction alerts across government, both to organisations and individuals on existing distribution lists, and those not on a distribution list but to whom the information is relevant.

Context and scope

Currently, conjunction and re-entry alerts have to be manually shared by the UKSA team to relevant groups across government via email.

Automatic sharing of alerts with government users according to pre-defined distribution criteria would improve access to information and save time for UKSA. Meanwhile, manual sending of alerts is still required in exceptional circumstances - such as a high risk to UK satellites or infrastructure - where additional users need to be notified.

Goals and non-goals

Goals:

  • Ensure that re-entry and conjunction alerts can be automatically sent to relevant government users should they meet pre-determined distribution criteria
  • Ensure distribution criteria are appropriate for the recipients of alerts
  • Ensure the UKSA team can manually choose to send an alert to government users, including both those on existing distribution lists and those not currently on them
  • Ensure manual sending of alerts can be performed repeatedly if necessary

Non-goals:

  • Functionality to remove individuals or organisations from automatic alert notifications
  • Functionality to adapt distribution criteria

The actual design

Criteria for escalating an event to an alert

Monitor Space Hazards will ingest CDMs and TIPs from Space Track, meaning it will include data on all observed events worldwide. However, only a small proportion of these events will be escalated to an alert. Events can be escalated to either a Level 1 (Standard) alert, or a Level 2 (Priority) alert. Level 1 and Level 2 alerts are sent to separate distribution lists of government users, but an event may be escalated to both levels simultaneously. The criteria for escalating events to either a Level 1 (Standard) or Level 2 (Priority) alert are as follows:

Conjunctions:

For Level 1 (Standard) alerts:

  • For UK-licensed objects:
    • Less than 5 days until Time of Closest Approach, and
    • More than 0.1% probability of collision, and
    • Press interest
  • For non-UK objects:
    • Less than 5 days until Time of Closest Approach, and
    • Classified as Low Risk or higher, and
    • No manoeuvre expected, and
  • For all objects:
    • Nominated for escalation by the National Space Operations Centre

For Level 2 (Priority) alerts:

  • For UK-licensed objects:
    • More than 1% probability of collision, and
    • No manoeuvre expected
  • For non-UK objects:
    • More than 5% probability of collision, and
    • No manoeuvre expected, and
    • Significant press interest

Re-entries:

For Level 1 (Standard) alerts:

  • Less than 36 hours until re-entry, and
  • One or more of the following:
    • Any “large” object in US SATCAT (except designed for demise) with overflights of the UK mainland, and/or
    • Any “large” object in US SATCAT (except designed for demise) with more than 0.1% chance of impact in overseas territories, and/or
    • Press interest, and/or
    • Nominated for escalation by the National Space Operations Centre

For Level 2 (Priority) alerts:

  • Debris likely to survive to the ground, and
  • One or more of the following:
    • More than 0.1% chance of impact in the UK (and overseas territories on case by case basis), and/or
    • UK-licensed object, and/or *Significant press interest

Fragmentations:

For Level 1 (Standard) alerts:

  • The criteria for Level 1 (Standard) alerts will be displayed here once confirmed by NSpOC.

For Level 2 (Priority) alerts (Fragmentation events are distributed to Level 2 (Priority) users by default):

  • More than 5% increase in potential collisions with UK satellites and/or Human Spaceflight missions, or
  • Significant press interest

Convention for Conjunctions and Re-entry events

Event level Author Permissions to view Conjunction Events (xxxxxxx-yyyyyyy-zzzzzz) Re-entry Events (REYY-0000) Fragmentation Events (FGYY-0000)
Input File type Language Recipients Input File type Language Recipients Input File type Language Recipients
Basic event Space-Track/Orbital Analysts All CDM Notification Operators TIP (Space-Track or UKSA created) Notification N/A None Notification N/A
Enhanced event Orbital Analysts All Orbital Analyst Analysis & Manoeuvre Trade-Space Plot JSON Notification Operators N/A N/A N/A N/A N/A N/A
Level 1 (Standard) alert Orbital Analysts (+ Approver comments) Government Organisations, Regulators and Agency Conjunction Report JSON (CR) + Conjunction event DB edits Alert Some Government Users Re-entry report JSON (RER) + Re-entry event DB edits Alert Some Government Users Fragmentation report JSON (FR) + Fragmentation event DB edits Alert Some Government Users
Level 2 (Priority) alert Orbital Analysts (+ Approver comments) Government Organisations, Regulators and Agency Conjunction Report JSON (CR) + Conjunction event DB edits Alert Some Government Users Re-entry report JSON (RER) + Re-entry event DB edits Alert Some Government Users Fragmentation report JSON (FR) + Fragmentation event DB edits Alert Some Government Users

Manual sending of notifications

The UKSA SST team, as an Approver user type (see 013 Permissions Model), may also manually send notifications about events to government users in cases where there is significant political or press interest. A user has the option to either send to a distribution list and/or send to selected email addresses that they input into a free text box. Once reviewed, this will send an email to the selected users informing them about the re-entry or conjunction alert.

Alternatives considered

We also considered enabling users to set their own criteria for when they receive notifications. The option was discounted because:

  • Users expressed concern that they would not know how to set their thresholds for notifications
  • Different users across government receiving different notifications could result in a confused response
  • The logic of the criteria for sending notifications is sufficiently complicated that it would result in a confusing user interface
This page was last reviewed on 16 February 2026. It needs to be reviewed again on 16 February 2027 .
This page was set to be reviewed before 16 February 2027. This might mean the content is out of date.