Satellite Scenario Icons to identify Orbit type and Orbit status

None

SSO

The SSO orbit is characterized by the Repeat Cycle (days) and the Cycle Length (orbits).

Every Repeat Cycle the satellite will be located at exactly the same position on Earth and obtain exactly the same swath foot print.

SSO with

MLST drift

Exact Repeat

The Exact Repeat orbit is characterized by the Repeat Cycle (days), the Cycle Length (orbits), and the Mean Local Solar Time Drift (seconds / day). Every Repeat Cycle the satellite will be located at exactly the same position on Earth and obtain exactly the same swath foot print, but the footprint times will be time-separated by the RC (days) corrected by MLST Drift

Future SSO

Future Exact Repeat

None

SSO

The warning is raised if the TLE orbit period and the SSO orbit period (from Repeat Cycle and Cycle length) depart from 0.2 seconds.

Exact Repeat

Future SSO

Future Exact Repeat

No icon: This orbit is configured with TLEs without any further qualification, and is accurate within few days of Epoch, typically 7 days.

TLE orbit with a warning flag. It indicates that the orbit Epoch is too old for accurate predictions. The flag is raised if the difference between TLE Epoch and current time is larger than 7 days (configurable via Edit / Properties / Satellites / Orbit).

To remove the warning try updating the TLEs online, or otherwise change the warning threshold.

SSO orbit, backed with TLEs. It is assumed that the satellite will execute OKMs to maintain the SSO nominal orbit. The TLEs provide a backbone for orbit calculation, but the result is slightly corrected to take into account the OKMs.

This orbit model is suitable for long term planning provided the operator will respect the SSO design. SaVoir will monitor this fact and raise a warning if the satellite operation departs from SSO design.

Exact Repeat orbit, backed with TLEs.

See same remarks as above for SSO orbits. Exact Repeat orbit requires also defining the MLST drift (sec/day)

SSO orbit backed with TLEs and a warning flag. The warning is raised if the TLE orbit period and the SSO orbit period (from Repeat Cycle and Cycle length) depart from 0.2 seconds.

To remove the warning try the following actions:

• Update TLEs online
• Modify the SSO parameters (Repeat Cycle and Cycle Length) to suit the new orbit period.
• Switch to another orbit source, e.g. pure TLE.

Exact Repeat orbit backed with TLEs and a warning flag. .

See same remarks as above for SSO orbits.

Nominal Orbit using Keplerian or Cartesian orbit elements. The orbit uses a simplified orbit calculator with J2 propagation model. Orbit is accurate within few days of Epoch, typically 4 days.

SSO orbit, backed with nominal Keplerian or Cartesian orbit elements. It is assumed that the satellite will execute OKMs to maintain the SSO nominal orbit.

The J2 propagator provides a backbone for orbit calculation, with the result slightly corrected to account for OKMs.

This orbit model is suitable for long term planning provided the operator will respect the SSO design. SaVoir will monitor this fact and raise a warning if the satellite operation departs from SSO design.

The Nominal Orbit allows to coordinate SaVoir output with the output of some satellite planning tools, e.g. Radarsat-1 and 2.

Exact Repeat Orbit, backed with nominal Keplerian or Cartesian orbit elements.

See same remarks as above for SSO orbits.

SSO Future orbit. Sometimes it is not possible to access valid TLEs or OSVs (Keplerian or Cartesian). The satellite has not yet been launched and the orbit design is loosely defined with parameters like Repeat Cycle, Cycle Length, Mean Local Solar Time, etc. In this case SaVoir can generate a usable nominal orbit which is by design perfectly matching the SSO definition.

Exact Repeat Future orbit

See same remarks as above for SSO orbits. Exact Repeat Future orbit requires also defining the MLST drift (sec/day)

Nominal Orbit with warning flag. It indicates that the orbit Epoch is too old for accurate predictions. The flag is raised if the difference between Orbit Epoch and current time is larger than 7 days (configurable via Edit / Properties / Satellites / Orbit).

To remove the warning try finding more accurate orbit elements, or otherwise change the warning threshold.

To remove the warning try the following actions:

• Find more accurate orbit elements
• Modify the SSO parameters (Repeat Cycle and Cycle Length) to suit the new orbit period.

Exact Repeat orbit, backed with nominal Keplerian or Cartesian orbit elements.

See same remarks as above for SSO orbits.

The orbit is defined with an Orbit File, according to several possible formats:

- XML Earth Explorer Reference Orbit Files (MPL_ORBREF)

- XML Earth Explorer Reference Orbit Scenario File (MPL_ORBSCT)

- Envisat Reference Orbit Event File (MPL_ORB_EVTRGT)

- Envisat Orbit Scenario File (MPL_ORB_SCVRGT)

- Two Line Element historical sets, as a continuous sequence of <Line1><Line2>