Spacecraft.CloseApproachRange(Variable, Spacecraft, Variable) Method

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Description

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

 

For more information on the Alfano/Negron Close Approach Software (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,

Spacecraft rangingSpacecraft,

Variable Algorithm)

 

 

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

 

 

rangingSpacecraft

Description:

Spacecraft 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.

 

 

 

 

Return Value

Type:

string

 

 

Returns a sequential listing of events related to the proximity of two objects.

 

The FF_Preferences.IntervalEventReportingBehavior property controls whether the start and end of propagation are reported as events. 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. If the close approach extends past the end of the propagation span, FreeFlyer labels the end of propagation as the end of the close approach.

 

Syntax

myString1 = mySpacecraft1.CloseApproachRange(myVariable1, mySpacecraft2, myVariable2);

 

 

Example 1

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

 

Spacecraft Spacecraft1;

Spacecraft Spacecraft2;

 

// Configure Spacecraft orbit

Spacecraft2.I = -Spacecraft1.I;

Spacecraft2.TA = Spacecraft1.TA + 5;

 

// *** For Millisecond Mode Only ***

While (Spacecraft1.ElapsedDays < 1);

 

          Report Spacecraft1.CloseApproachRange(100, Spacecraft2, 0) to "SC_CloseApproach.txt";

          Step Spacecraft1;

          Step Spacecraft2 to (Spacecraft2.Epoch == Spacecraft1.Epoch);

 

End;

 

Or

 

// *** For Nanosecond Mode Only ***

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

 

          Report Spacecraft1.CloseApproachRange(100, Spacecraft2, 0) to "SC_CloseApproach.txt";

          Step Spacecraft1;

          Step Spacecraft2 to (Spacecraft2.Epoch == Spacecraft1.Epoch);

 

End;

 

 

Output:

 

Note: Output generated using nanosecond timing precision mode.

 

Range Calculated by ANCAS #1 Algorithm

 

Range Event                              Epoch                             Range (Km)         Duration (Min)

Spacecraft2 -> Spacecraft1 Start Check   Jan 01 2020 00:00:00.000000000    4166.581065867

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 00:20:00.079974425   14025.828838720

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 08:09:46.852888670     100.000000000

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 08:10:00.055868400      83.384335234

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 08:10:13.265616358     100.000000000       0.440212128

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 08:34:45.932550118   14025.772753528

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 23:49:50.035709984     100.000000000     939.612834894

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 23:50:00.802202940      88.860355675

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 23:50:11.638767730     100.000000000       0.360050962

Spacecraft2 -> Spacecraft1 Maximum       Jan 02 2020 00:00:00.000000000    8282.403558159

Spacecraft2 -> Spacecraft1 End Check     Jan 02 2020 00:00:00.000000000    8282.403558159

 

 

 

 

 

Example 2

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

 

Spacecraft Spacecraft1;

Spacecraft Spacecraft2;

 

// Configure Spacecraft orbit

Spacecraft2.I = -Spacecraft1.I;

Spacecraft2.TA = Spacecraft1.TA + 5;

 

// *** For Millisecond Mode Only ***

While (Spacecraft1.ElapsedDays < 1);

 

          Report Spacecraft1.CloseApproachRange(100, Spacecraft2, 1) to "SC_CloseApproach.txt";

          Step Spacecraft1;

          Step Spacecraft2 to (Spacecraft2.Epoch == Spacecraft1.Epoch);

 

End;

 

Or

 

// *** For Nanosecond Mode Only ***

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

 

          Report Spacecraft1.CloseApproachRange(100, Spacecraft2, 1) to "SC_CloseApproach.txt";

          Step Spacecraft1;

          Step Spacecraft2 to (Spacecraft2.Epoch == Spacecraft1.Epoch);

 

End;

 

 

Output:

 

Note: Output generated using nanosecond timing precision mode.

 

Range Calculated by ANCAS #2 Algorithm

 

Range Event                              Epoch                             Range (Km)         Duration (Min)

Spacecraft2 -> Spacecraft1 Start Check   Jan 01 2020 00:00:00.000000000    4166.581065867

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 00:20:00.092903614   14025.828854206

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 00:44:44.746275869     100.000000000

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 00:44:44.746275902      87.889483700

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 00:44:59.999999943     100.000000000       0.254228735

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 01:09:28.242472172   14017.231841976

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 01:34:12.083876074     100.000000000      49.201397936

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 01:34:12.083876133      87.428001681

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 01:34:59.999999955     100.000000000       0.798602065

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 01:58:57.059269428   14025.634058280

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 02:23:41.689693399     100.000000000      48.694828224

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 02:23:41.689693451      86.858070495

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 02:24:59.999999964     100.000000000       1.305171776

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 02:48:25.202068806   14017.296673141

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 03:13:09.057980493     100.000000000      48.150966342

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 03:13:09.057980537      86.432243821

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 03:14:59.999999948     100.000000000       1.849033658

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 03:37:54.044877052   14025.667612740

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 04:02:32.687170398     100.000000000      47.544786174

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 04:02:38.690922260      85.883369825

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 04:04:59.999999967     100.000000000       2.455213826

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 04:27:22.206950665   14017.286044109

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 04:52:06.061072767     100.000000000      47.101017880

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 04:52:06.061072826      85.477347489

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 04:54:59.999999960     100.000000000       2.898982120

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 05:16:51.068238735   14025.838226053

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 05:41:35.738573506     100.000000000      46.595642892

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 05:41:35.738573551      84.857214317

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 05:44:59.999999952     100.000000000       3.404357107

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 06:06:19.259450912   14017.374541146

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 06:31:03.115420282     100.000000000      46.051923672

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 06:31:03.115420341      84.435918762

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 06:34:59.999999945     100.000000000       3.948076328

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 06:55:48.127767563   14025.954045814

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 07:20:32.807815044     100.000000000      45.546796918

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 07:20:32.807815075      83.725431099

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 07:24:59.999999969     100.000000000       4.453203082

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 07:45:16.352771282   14017.580869780

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 08:09:26.335802909     100.000000000      44.438930049

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 08:10:00.232367039      83.313252194

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 08:10:35.191716382     100.000000000       1.147598558

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 08:34:45.232761383   14025.881157635

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 08:59:29.903819530     100.000000000      48.911868386

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 08:59:29.903819561      82.604835282

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 08:59:59.999999944     100.000000000       0.501603007

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 09:24:13.463521957   14017.648448075

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 09:48:57.348162119     100.000000000      48.955802703

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 09:48:57.348162174      82.252502870

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 09:49:59.999999942     100.000000000       1.044197297

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 10:13:42.324660778   14025.719289048

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 10:37:58.741581954     100.000000000      47.979026367

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 10:38:26.981205463      81.636585181

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 10:39:59.999999957     100.000000000       2.020973633

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 11:03:10.527283192   14017.443413540

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 11:27:40.793681152     100.000000000      47.679894687

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 11:27:54.391671658      81.329707662

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 11:29:59.999999942     100.000000000       2.320105313

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 11:52:39.369242191   14025.681918315

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 12:17:24.030548062     100.000000000      47.400509135

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 12:17:24.030548096      80.791122846

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 12:19:59.999999964     100.000000000       2.599490865

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 12:42:07.545021534   14017.160473996

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 13:06:51.375361867     100.000000000      46.856256032

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 13:06:51.375361919      80.453756064

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 13:09:59.999999956     100.000000000       3.143743968

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 13:31:36.364186764   14025.761434034

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 13:56:21.032909832     100.000000000      46.350548498

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 13:56:21.032909870      79.909174427

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 13:59:59.999999949     100.000000000       3.649451502

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 14:21:04.525565624   14017.046322974

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 14:45:48.339268163     100.000000000      45.805654470

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 14:45:48.339268208      79.502783987

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 14:49:59.999999941     100.000000000       4.194345530

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 15:10:33.328329563   14025.774943763

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 15:35:17.989956822     100.000000000      45.299832615

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 15:35:17.989956856      78.910213342

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 15:39:59.999999967     100.000000000       4.700167386

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 16:00:01.494250298   14017.151872609

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 16:23:57.769412784     100.000000000      43.962823547

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 16:24:45.329936504      78.495802733

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 16:24:59.999999945     100.000000000       1.037176453

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 16:49:30.317148685   14025.740612278

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 17:14:14.967729033     100.000000000      49.249462151

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 17:14:14.967729092      77.888033650

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 17:14:59.999999958     100.000000000       0.750537849

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 17:38:58.493892670   14017.353035160

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 18:03:42.360677667     100.000000000      48.706011295

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 18:03:42.360677719      77.553551150

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 18:04:59.999999964     100.000000000       1.293988705

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 18:28:27.366224289   14025.843625624

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 18:53:12.030608609     100.000000000      48.200510144

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 18:53:12.030608654      76.963431526

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 18:54:59.999999950     100.000000000       1.799489856

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 19:17:55.571437836   14017.455441906

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 19:42:32.650016292     100.000000000      47.544166939

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 19:42:39.460997581      76.709555882

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 19:44:59.999999967     100.000000000       2.455833061

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 20:07:24.499084473   14026.029263672

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 20:32:09.186296433     100.000000000      47.153104941

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 20:32:09.186296463      76.111591723

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 20:34:59.999999960     100.000000000       2.846895059

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 20:56:52.708334923   14017.367443815

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 21:21:36.587367966     100.000000000      46.609789467

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 21:21:36.587368011      75.844755796

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 21:24:59.999999953     100.000000000       3.390210533

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 21:46:21.627643585   14026.020619240

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 22:11:06.303877323     100.000000000      46.105064623

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 22:11:06.303877354      75.196030969

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 22:14:59.999999946     100.000000000       3.894935377

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 22:35:49.796620846   14017.238373305

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 23:00:33.657642334     100.000000000      45.560960706

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 23:00:33.657642365      74.836629184

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 23:04:59.999999969     100.000000000       4.439039294

Spacecraft2 -> Spacecraft1 Maximum       Jan 01 2020 23:25:18.666876316   14025.752738941

Spacecraft2 -> Spacecraft1 Entry         Jan 01 2020 23:49:36.774267701     100.000000000      44.612904462

Spacecraft2 -> Spacecraft1 Minimum       Jan 01 2020 23:50:03.304202080      74.157392490

Spacecraft2 -> Spacecraft1 Exit          Jan 01 2020 23:50:44.946040527     100.000000000       1.136196214

 

 

 

See also

Spacecraft Object

Spacecraft.CloseApproachRange

Spacecraft Propagation Guide

Coverage and Contact Analysis Guide