Measuring System Response Time
- A request for collection is received (during animation this is the current time).
- Command generation (CommandPrepTime seconds required for command gen).
- Uplink from command station – possible at end of command gen if currently in access and at least CommandTime remains in access interval. Otherwise, this has to wait until a command station access of at least CommandTime occurs.
- Asset prepares to collect (requires PreCollectDelay seconds from end of commanding).
- Asset makes collection (CollectionTime required prior to end of access period) – possible at end of PreCollectDelay if currently in access. Otherwise, this has to wait until a grid point access of at least CollectionTime occurs.
- Asset prepares to downlink data (requires PostCollectDelay seconds from end of collection).
- Downlink of data – possible at end of PostCollectDelay if currently in access and at least DownlinkTime remains in access interval. Otherwise, this has to wait until a receive station access of at least DownlinkTime occurs.
The computation of System Response Time is illustrated in the following figure.
Asset* - If sub-objects (Sensors, Receivers, Transmitters, etc.) are assigned as assets, command window generation is performed based on access to the parent object.
The overall system response time is then computed as: (Time of completion of data downlink – Time of collection request). The dynamic value of System Response Time can be zero only if all delays are set to zero and if simultaneous access exists between a command station, the collection asset and a receive station. Options for the static definition of System Response Time are described in the following table.
Compute options for System Response Time
| Option | Description |
|---|---|
| Average | The average system response time over the entire coverage interval. The average is computed by sampling the coverage analysis interval at the input step size. Samples where the system response time cannot be computed due to the coverage analysis interval ending before the downlink of data can be completed are not used in the computation of the average. |
| Maximum | The maximum system response time over the entire coverage interval. The result will be equal to the time between the last possible time when the data downlink can be completed during the coverage analysis interval and the end of the coverage analysis interval, if this span is larger than any other response time encountered. |
| Minimum | The minimum response time over the entire coverage interval. The value is 0 only if all delay times are equal to 0 and simultaneous access exists for all required communication paths. |
Command Object
Specify the object(s) from which commands can be generated and uplinked to assets to schedule collections. A Constellation object can be specified if more than one command object is desired. Note that Constellation operators are not currently honored.
If sub-objects (Sensors, Receivers, Transmitters, etc.) are assigned as assets, command window generation is performed based on access to the parent object.
Receive Object
Specify the object(s) to which collected data can be transmitted from assets. A Constellation object can be specified if more than one receive object is desired. Note: Constellation operators are not currently honored.
If sub-objects (Sensors, Receivers, Transmitters, etc.) are assigned as assets, receive window generation is performed based on access to the parent object.
Command Prep Time
Specify the amount of time required to generate collection commands prior to uplink of the commands from the command object(s) to the assets.
Commanding Time
Specify the amount of time required to uplink generated collection commands from the command object(s) to the assets.
Pre-collection Time
Specify the amount of time required to configure an asset for collection after the collection command has been received.
Collection Time
Specify the amount of time required for an asset to perform a collection after it has been properly configured.
Post-collection Time
Specify the amount of time required to configure an asset for downlink after the collection has been completed.
Downlink Time
Specify the amount of time required to downlink generated data after the asset has been configured for downlink.
Allow Forward Crosslink
Specify if a single forward crosslink is to be allowed for commanding assets. The use of forward crosslinks allows a collection command to be passed from one asset to another which will actually do the collection. The collecting asset then downlinks the collected data. There is not currently an option for a return crosslink.
If sub-objects (Sensors, Receivers, Transmitters, etc.) are assigned as assets, crosslink window generation is performed based on access between parent objects.
Time Step
Specify the amount time to be used in computing the average value of the system response time. Only used during the computation of satisfaction intervals for compute options other than Average.
Displaying System Response Time in a Graphics Window
Graphics are used to represent the static and dynamic value of System Response Time. Graphics representing the dynamic values are only displayed during animation. If Satisfaction is enabled, the graphics follow the general behavior for satisfaction graphics. If Satisfaction is disabled, the graphics appear as described in the following table:
| Static or Animation? | Grid points highlighted if they... |
|---|---|
| Static | Have a non-zero system response time at some point |
| Animation | Have a non-zero system response time at the current time |
The Satisfaction Threshold value is the time between a request for coverage of a point and the achievement of that request. The default behavior for this Figure Of Merit corresponds to a Satisfaction setting of Greater Than 0.
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