Constraining a Constellation

Constellation constraints enable you to specify the criteria to be used when constellations are combined with other objects in a chain. Each pair of objects in the chain can be thought of as creating access pairs with a "from" object and a "to" object. Constellation constraints enable you to specify different logical and parent ownership constraints, depending on where the constellation sits in the chain, either as the "from" object or the "to" object.

Restrictions

Select one of the following from the Restriction drop-down list:

Any of

EITHER/OR criterion: The constraint is satisfied if any one object in the constellation meets the conditions for chain access. For example, consider a constellation meeting both of the following conditions:

  • is defined as a group of three ground stations A, B, and C
  • belongs to a chain with a single satellite

Then the constraint is satisfied when the satellite can access ground station A or ground station B or ground station C.

All of

AND criterion: The constraint is satisfied if all objects in the constellation meet the conditions for chain access. For example, consider a constellation that meets both of the following conditions:

  • is defined as a group of three ground stations A, B, and C
  • belongs to a chain with a single satellite

Then the constraint is satisfied when the satellite can access ground station A and ground station B and ground station C simultaneously. This is sometimes called "coincident coverage."

At Least N

AND/OR criterion: The constraint is satisfied if at least the specified number of objects in the constellation meet the conditions for chain access. In the text box to the right of the Restriction list, enter the minimum number of objects that must meet those conditions. For example, you could set the minimum number to 2 and consider when the constellation meets the following conditions:

  • is defined as a group of three ground stations A, B, and C
  • belongs to a chain with a single satellite

Then the constraint is satisfied when the satellite can access any of the following combinations of ground stations:

  • A and B
  • A and C
  • B and C
  • A and B and C

Another good example of this criterion is the Global Positioning System (GPS), for which you could specify At Least 4.

Exactly N

ONLY criterion: This constraint is satisfied if the exact specified number of objects in the constellation meets the conditions for chain access. In the text box to the right of the Restriction list, enter the exact number of objects that must meet those conditions. For example, you could set the exact number to 2 and consider when the constellation meets the following conditions:

  • is defined as a group of three ground stations A, B, and C
  • belongs to a chain with a single satellite

Then the constraint is satisfied when the satellite can access the following pairs of ground stations:

  • A and B
  • B and C
  • A and C

but NOT all three together:

  • A and B and C

None Of

ONLY criterion: The constraint is satisfied if NO objects in the constellation meet the conditions for chain access. The results of this constraint are available only in the Complete Chain Access report or graph.

If two constellations are part of a chain link and either constellation uses the NoneOf option, the NoneOf constraint will take precedence and the logical constraint on the other constellation will be ignored.

Parent Platform Restriction

Use the Parent Platform Restriction options to constrain constellations of child objects.

Option Description
'From' access position Select one of the following options:

  • No Restriction. A child object on a given satellite is allowed to link from another child object on any satellite.

  • Different Parents. A child object on a given satellite is allowed to link only from another child object on a different satellite.

  • Same Parents. A child object on a given satellite is allowed to link only from another child object on the same satellite.
'To' access position Select one of the following options:

  • No Restriction. A child object on a given satellite is allowed to link to another child object on any satellite.

  • Different Parents. A child object on a given satellite is allowed to link only to another child object on a different satellite.

  • Same Parents. A child object on a given satellite is allowed to link only to another child object on the same satellite.

The Parent Platform Restriction options apply to sensors, receivers, transmitters, and radars.