CDM Comparison
CDM comparison shows how each mitigation plan for a conjunction event would change its risk. Every mitigation plan is reported beside a single reference CDM in the same risk metrics and the same B-plane and encounter-plane plots, so the effect of acting on it is measurable before committing to it.
Pc can only be calculated when both primary and secondary states at TCA include covariance. Uploading an ephemeris without covariance will produce a CDM that reports miss distance alone.
Getting Started
- Select a reference CDM from the CDM timeline.
- Upload an ephemeris, or generate a plan in Maneuver Designer.
- Choose which mitigation plans to compare.
- Identify the mitigation plan that best reduces the risk.
A mitigation plan can also be submitted as a screening job to identify how it affects close approaches with other secondary RSOs.
Selecting a Reference CDM
The reference CDM is the conjunction event's currently selected CDM from the timeline. This CDM is used as a reference to compare against each mitigation plan, and can be switched out by selecting a different timeline CDM.
Uploaded ephemeris and generated maneuvers use the currently selected CDM for the secondary state and covariance data. The mitigation plan's linked CDM ID is listed under the Source column.
Adding a Mitigation Plan
A mitigation plan is added either by uploading an ephemeris or by generating one in Satcat's Maneuver Designer. Both produce a theoretical CDM that appears in the comparison and on the conjunction event's CDM timeline, and both remain private to the operator's organization unless the underlying ephemeris is operational.
Uploaded ephemeris is available to all Satcat Operations users. Maneuver Designer requires a Pro or Enterprise subscription. To learn more, see Maneuver Designer.
Uploading an Ephemeris
Upload an OPM or OEM for the primary RSO. The ephemeris must cover the conjunction event's TCA, since the comparison is evaluated at that time.
Uploaded ephemeris carries a CONTEXT metadata field that broadcasts its purpose to other operators. Examples of context values include ROUTINE for a non-maneuvering RSO, COLA for collision avoidance, or MAINTENANCE for preplanned orbit maintenance. The context remains with the ephemeris and signals RSO intent to other operators if the ephemeris is later made operational.
See Mitigation Intent Signaling for more information.
Generating a Plan in Maneuver Designer
Generate a High-Fidelity Plan from a selected maneuver chosen from the maneuver tradespace. Satcat propagates these plans at the highest available fidelity, recalculates the post-maneuver risk metrics, and writes the OPM that becomes the mitigation plan. These plans are then surfaced in the originating conjunction event as Theoretical CDMs.
Comparing Mitigation Plans
The reference CDM is always shown as a baseline to compare mitigation plans against. The three most recently created plans are included in the comparison by default; use Manage plans to select additional mitigation plans to compare. Each selected mitigation plan is shown in the comparison table with a summary of the predicted risk metrics expected from implementing the plan.
The plot under the table presents the same comparison using encounter plane geometry, which is useful for seeing the relative effects of mitigation plans. Each CDM is plotted independently with its secondary at the origin, which keeps plans comparable even though a plan moves the primary and shifts its TCA.
To learn more about how each projection is constructed, see B-plane and Encounter Plane.
How New CDMs Affect Results
A mitigation plan's results are fixed when the plan is created, using the secondary state and covariance of the CDM selected at that time. New CDMs that arrive after the mitigation plan is created are not recomputed or reflected in the existing results. New mitigation plan results will need to be generated against new CDM data.
Selecting a newer CDM changes what results are measured against without changing the results themselves, so a plan created against an earlier CDM is compared to a reference it was not screened against. A plan created before the latest tracking data arrived also does not account for that data.
Evaluating an ephemeris against newer tracking data requires adding it again with the newer CDM selected.
Enacting a Mitigation Plan
Comparing a plan does not commit to it. To enact one, upload the maneuver's ephemeris with an OPERATIONAL designation. Satcat updates the conjunction event with the new ephemeris and signals the RSO's mitigation intent to the other operator.
Rate limiting applies to ROUTINE ephemeris only, at one conjunction event update every 30 minutes. COLA and MAINTENANCE ephemeris take effect without that delay. See Asset Management for an RSO's latest operational files.