An anomaly pass is a contact window where the goal is not routine operations, but rapid diagnosis and safe recovery. Whether the issue is degraded RF, unexpected telemetry, attitude problems, power constraints, or a partial communications failure, the pass is usually short, stressful, and information-dense. A strong anomaly pass playbook helps operators capture the right evidence, take safe actions, and avoid making the situation worse.
Table of contents
- What Is an Anomaly Pass?
- Goals of an Anomaly Pass
- What to Log During an Anomaly Pass
- How to Act: The Core Response Pattern
- Command Discipline and Safety Guardrails
- RF Triage: What to Check First
- Telemetry Triage: What to Check First
- Handoffs and Escalation
- Post-Pass Actions and Incident Records
- Anomaly Pass Playbooks FAQ
- Glossary
What Is an Anomaly Pass?
An anomaly pass is a scheduled or ad-hoc contact window used to investigate and respond to abnormal spacecraft behavior or ground segment issues. The pass may be initiated because of an alarm (loss of signal, missed telemetry), suspicious trends (battery discharge, temperature drift), unexpected spacecraft mode changes, or environmental events (high radiation, conjunction avoidance maneuvers).
Unlike routine passes, anomaly passes are often executed under time pressure, with incomplete information and evolving hypotheses. That’s why playbooks focus on disciplined logging, safe actions, and clear decision points.
Goals of an Anomaly Pass
An anomaly pass typically has four goals, in priority order:
1) Protect the spacecraft: 2) Restore minimum viable communications: 3) Gather high-quality evidence: 4) Enable a recovery plan:
A good playbook makes it clear when to stop “trying things” and shift into evidence collection and escalation.
What to Log During an Anomaly Pass
High-quality logs are often the most valuable output of an anomaly pass. Operators should capture:
Pass context and timeline
UTC timestamps: Station and configuration: Predicted geometry: Mission context:
RF observations
Carrier presence: Frequency and Doppler behavior: Signal quality: Spectrum evidence: Pointing and tracking: Polarization and path:
Telemetry and data integrity
Telemetry frames received: Key subsystem health: Mode/state indicators: Command outcomes:
Operator actions and system changes
Every change made: Commands sent: Observed result:
How to Act: The Core Response Pattern
The most reliable anomaly-pass behavior is a repeatable pattern:
1) Stabilize: 2) Verify reality: 3) Minimize changes: 4) Capture evidence continuously: 5) Escalate early:
If multiple people are involved, separate roles: one person drives actions, one person logs, and one person communicates with stakeholders.
Command Discipline and Safety Guardrails
Commands can help recovery—or cause irreversible damage. An anomaly playbook should include strict guardrails:
Use approved command sets: Prefer read-only first: One change at a time: Respect inhibit lists: Confirm addressing and timing:
If you are uncertain whether a command is safe, the correct action is usually to stop and escalate—while continuing to collect telemetry and RF evidence.
RF Triage: What to Check First
Many “spacecraft anomalies” are actually RF or configuration problems. A fast RF triage sequence usually includes:
Confirm the obvious: Confirm tracking: Check frequency plan: Look at the spectrum: Test known-good references:
The playbook should define when frequency “hunting” is allowed and how wide the search can go before it becomes counterproductive.
Telemetry Triage: What to Check First
If you have telemetry, prioritize the signals that indicate immediate risk:
Power: Thermal: Attitude/orbit: Comms state: Computer health:
The playbook should specify “stop conditions” (e.g., power near critical thresholds) where actions must shift from investigation to immediate stabilization.
Handoffs and Escalation
An anomaly pass rarely ends with a full fix. Strong playbooks make handoffs clean:
Escalate with a short summary: Attach evidence: State impact clearly: Set the next action:
The goal is that the next team can pick up without re-discovering the basics.
Post-Pass Actions and Incident Records
After the pass, convert raw logs into an incident record:
Timeline: Observed vs expected: Actions and outcomes: Hypotheses: Next steps:
When the incident is over, update the playbook. An anomaly playbook that doesn’t improve over time is just a document, not a capability.
Anomaly Pass Playbooks FAQ
What’s the most important thing to log if the pass is short?
A precise timeline plus RF evidence. Even a short spectrum capture with timestamps and configuration details can be the difference between guessing and knowing.
How do I avoid making the anomaly worse?
Minimize changes, follow command guardrails, and prioritize read-only telemetry first. If you are uncertain about command safety, escalate while continuing evidence capture.
Should operators troubleshoot RF before assuming spacecraft failure?
Yes. Confirm station configuration, pointing, frequency/Doppler, and interference conditions early. Many “spacecraft issues” turn out to be ground-side mismatches.
When should I stop trying fixes and just collect data?
When actions become speculative, when risk is high, or when time is too short to safely validate changes. In those cases, focus on high-quality logs and set up the next pass with a clear plan.
Glossary
Anomaly pass: A contact window executed to investigate or respond to abnormal spacecraft or ground segment behavior.
AOS/LOS: Acquisition of Signal / Loss of Signal—the start and end of a satellite contact window.
TT&C: Telemetry, Tracking, and Command—core functions used to monitor and control a spacecraft.
Eb/No: Energy per bit to noise density; commonly used to assess digital link quality.
C/N0: Carrier-to-noise density; a signal quality metric often used in satellite links.
BER/PER: Bit Error Rate / Packet Error Rate—measures of data integrity under current link conditions.
Command discipline: Procedural safeguards that prevent unsafe or ambiguous command actions during recovery.
Interference: Unwanted RF energy that degrades reception or transmission performance.
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