Spacecraft.CloseApproachRange(Variable, GroundStation, Variable, TimeSpanArray, Array, Array) Method

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Description

Returns a sequential listing of events related to the proximity of the calling Spacecraft and the argument rangingStation using the specified Algorithm.

 

For more information on the ANCAS algorithms, please refer to: Alfano, Salvatore. Determining Satellite Close Approaches, Part II. Journal of the Astronautical Sciences 42.2. Apr-Jun 1994, 143-152.

 

Timing Precision Mode

This page describes functionality in nanosecond timing precision mode.

Click here to see the documentation for this object in millisecond timing precision mode.

 

Note: This is an interval method. See the Interval Methods page for more information.

Note: This method has a state. See the Methods and Properties with State page for more information.

 

Method Signature

Spacecraft.CloseApproachRange(

Variable rangeLimit,

GroundStation rangingStation,

Variable Algorithm,

TimeSpanArray EventTime,

Array EventType,

Array EventRange)

 

 

Arguments

rangeLimit

Description:

Range that specifies the distance inside of which the closest approach detection is desired and outside of which the greatest separation detection is desired.

Units:

km

 

 

rangingStation

Description:

GroundStation object with respect to which range is computed.

 

 

Algorithm

Description:

interpolationMethod.

Valid Values:

Value

Label

0

ANCAS 1 interpolation method. This method uses the position and velocity states from three data points to create a quintic polynomial approximating the range between the two objects over time.

1

ANCAS 2 interpolation method. This method uses the position, velocity, and acceleration states from two data points to create a quintic polynomial approximating the range between the two objects over time.

 

 

 

EventTime

Description:

The time that the event occurred.

 

The FF_Preferences.IntervalEventReportingBehavior property controls whether the start of propagation is reported as an event. By default, if the close approach starts before the beginning of the propagation span, FreeFlyer will label the start of the propagation as the start of the close approach.

 

 

EventType

Description:

The type of the event that occurred.

Event Type == 1 is Range Limit Entry Detected.

Event Type == 2 is Range Limit Exit Detected.

Event Type == 3 is Minimum Range Detected.

Event Type == 4 is Maximum Range Detected.

 

 

EventRange

Description:

The range between the two Objects' centers at the epoch when the event occurred.

 

 

 

Return Value

Type:

number

 

 

Returns the number of elements filled into EventType and EventTime arrays.

 

Syntax

myVariable1 = mySpacecraft1.CloseApproachRange(myVariable2, myGroundStation1, myVariable3, myTimeSpanArray1, myArray1, myArray2);

 

 

Example 1

This example demonstrates how to generate a report of events related to the proximity of the calling Spacecraft and rangingStation. The algorithm used is the ANCAS 1 interpolation method as specified when calling the method.

 

Spacecraft Spacecraft1;

GroundStation GroundStation1;

 

Variable i;

Variable numEvents;

Variable scEventRange;

TimeSpanArray EventTime;

Array EventType;

Array EventRange;

String scEventType;

String scEventTime;

DataTableWindow scReport({scEventType, scEventTime, scEventRange});

 

While (Spacecraft1.ElapsedTime < TIMESPAN(1 days));

 

          numEvents = Spacecraft1.CloseApproachRange(2000, GroundStation1, 0, EventTime, EventType, EventRange);

 

          If(numEvents > 0) then;

                      For i = 0 to numEvents - 1 step 1;

                                  Switch (EventType[i]);

                                              Case 1:

                                                          scEventType  = "Range Limit Entry Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                                          Break;

                                              Case 2:

                                                          scEventType  = "Range Limit Exit Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                                          Break;

                                              Case 3:

                                                          scEventType  = "Minimum Range Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                                          Break;

                                              Case 4:

                                                          scEventType  = "Maximum Range Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                  End;

                      End;

          End;

 

          Step Spacecraft1;

 

End;

 

 

Output:

 

scEventType

scEventTime

scEventRange

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Jan 01 2020 05:34:40.015518958

Jan 01 2020 06:20:40.668108757

Jan 01 2020 06:24:20.692254228

Jan 01 2020 06:27:20.675365448

Jan 01 2020 07:12:52.433894334

Jan 01 2020 07:58:04.553229058

Jan 01 2020 08:01:01.274696287

Jan 01 2020 08:04:41.807622744

Jan 01 2020 08:49:51.971603678

Jan 01 2020 17:22:50.273261095

Jan 01 2020 17:24:37.220907111

Jan 01 2020 17:26:13.895981968

Jan 01 2020 18:12:52.189776375

Jan 01 2020 18:57:28.927807113

Jan 01 2020 19:01:10.451257826

Jan 01 2020 19:05:56.683246379

13233.006219958

2000.000000000

1456.835268717

2000.000000000

13457.908284212

2000.000000000

1512.963152347

2000.000000000

13245.521449271

2000.000000000

1852.426632617

2000.000000000

13450.674641444

2000.000000000

1177.904365929

2000.000000000

 

 

 

Example 2

This example demonstrates how to generate a report of events related to the proximity of the calling Spacecraft and rangingStation. The algorithm used is the ANCAS 2 interpolation method as specified when calling the method.

 

Spacecraft Spacecraft1;

GroundStation GroundStation1;

 

Variable i;

Variable numEvents;

Variable scEventRange;

TimeSpanArray EventTime;

Array EventType;

Array EventRange;

String scEventType;

String scEventTime;

DataTableWindow scReport({scEventType, scEventTime, scEventRange});

 

While (Spacecraft1.ElapsedTime < TIMESPAN(1 days));

 

          numEvents = Spacecraft1.CloseApproachRange(2000, GroundStation1, 1, EventTime, EventType, EventRange);

 

          If(numEvents > 0) then;

                      For i = 0 to numEvents - 1 step 1;

                                  Switch (EventType[i]);

                                              Case 1:

                                                          scEventType  = "Range Limit Entry Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                                          Break;

                                              Case 2:

                                                          scEventType  = "Range Limit Exit Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                                          Break;

                                              Case 3:

                                                          scEventType  = "Minimum Range Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                                          Break;

                                              Case 4:

                                                          scEventType  = "Maximum Range Detected: ";

                                                          scEventTime  = EventTime[i].ConvertToCalendarDate();

                                                          scEventRange = EventRange[i];

                                                          Update scReport;

                                  End;

                      End;

          End;

 

          Step Spacecraft1;

 

End;

 

 

Output:

 

scEventType

scEventTime

scEventRange

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:

Maximum Range Detected:

Range Limit Entry Detected:

Minimum Range Detected:

Range Limit Exit Detected:  

Jan 01 2020 05:34:40.306632996

Jan 01 2020 06:21:13.582672665

Jan 01 2020 06:23:53.464618206

Jan 01 2020 06:27:25.935449784

Jan 01 2020 07:12:52.177662373

Jan 01 2020 07:57:49.838740036

Jan 01 2020 08:01:30.474245548

Jan 01 2020 08:04:07.096966335

Jan 01 2020 08:49:51.487457752

Jan 01 2020 17:22:23.225101742

Jan 01 2020 17:24:20.929784298

Jan 01 2020 17:26:52.498385960

Jan 01 2020 18:12:52.025874138

Jan 01 2020 18:57:32.726694464

Jan 01 2020 19:01:43.540703297

Jan 01 2020 19:06:30.785046306

13232.967472633

2000.000000000

1404.510626916

2000.000000000

13458.117824464

2000.000000000

1424.302485713

2000.000000000

13245.536220655

2000.000000000

1839.198555102

2000.000000000

13450.893995579

2000.000000000

1009.884828748

2000.000000000

 

 

 

See also

Spacecraft Object

Spacecraft.CloseApproachRange

Spacecraft Propagation Guide

Coverage and Contact Analysis Guide