Error loading TLE file into satellite object

Question

jose nuñez 2024-1-24

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https://ww2.mathworks.cn/matlabcentral/answers/2073931-error-loading-tle-file-into-satellite-object

评论： Andrew Mihalik 2024-7-23

I'm creating a GPS scenario loading current TLE into the satellite object with following commands:

% Create Scenario
startTime = datetime('now', 'Format', 'yyyy-MM-dd HH:mm:ss');
stopTime  = startTime;
sampleTime = 1;   % secs
sc = satelliteScenario(startTime,stopTime,sampleTime);
% Load TLE
websave('tledata.tle', 'https://celestrak.org/NORAD/elements/gp.php?GROUP=gps-ops&FORMAT=tle');
% Put satellites into the scenario
sats = satellite(sc,'tledata.tle');

But I obtain following error:

Error using satelliteScenario/satellite>throwExceptions

Unable to add satellite to the satelliteScenario.

Error in satelliteScenario/satellite

Caused by:

Incorrect size for expression 'time.fmt': expected [1x0] but found [1x19].

Has anyone an idea on what's going on? TLE file seems to be OK.

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Andrew Mihalik 2024-7-23

在 MATLAB Online 中打开

Hello, if we assume I ran the following code:

sc = satelliteScenario;
StartTime_datestring= '2024-07-22 17:52:39'
StopTime_datestring= '2024-08-23 17:52:39'

Can anyone explain why, then, this code executes correctly and without error:

StartTime_datetime=datetime(StartTime_datestring,'InputFormat','yyyy-MM-dd HH:mm:ss');
StopTime_datetime=datetime(StopTime_datestring,'InputFormat','yyyy-MM-dd HH:mm:ss');
sc.StartTime=StartTime_datetime
sc.StopTime=StopTime_datetime

But this code:

StartTime_datetime=datetime(StartTime_datestring,'Format','yyyy-MM-dd HH:mm:ss');
StopTime_datetime=datetime(StopTime_datestring,'Format','yyyy-MM-dd HH:mm:ss');
sc.StartTime=StartTime_datetime
sc.StopTime=StopTime_datetime

creates an error saying Incorrect size for expression 'time.fmt': expected [1x0] but found [1x19].

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Answer 1

Varun 2024-1-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2073931-error-loading-tle-file-into-satellite-object#answer_1398946

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Hi Jose,

Looks like the error is related to the size of the 'time.fmt' field in the TLE file. The expected size is [1x0], but the error indicates that it found [1x19].

I debugged the code and found that the error is occurring due to the first line because of using ‘Format’ name-value pair in the ‘datetime’ function:

startTime = datetime('now', 'Format', 'yyyy-MM-dd HH:mm:ss');

To resolve this error, you can simply replace this line with the following line which is independent of ‘Format’ name-value pair:

startTime = datetime('now');

Please refer to the following documentations to learn more:

‘datetime’: https://www.mathworks.com/help/matlab/ref/datetime.html

‘satelliteScenario’: https://www.mathworks.com/help/aerotbx/ug/satellitescenario.html

Hope it helps.

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jose nuñez 2024-1-30

thanks for your clarification!

Andrew Mihalik 2024-7-23

在 MATLAB Online 中打开

Hello, if we assume I ran the following code:

sc = satelliteScenario;
StartTime_datestring= '2024-07-22 17:52:39'
StopTime_datestring= '2024-08-23 17:52:39'

Can anyone explain why, then, this code executes correctly and without error:

StartTime_datetime=datetime(StartTime_datestring,'InputFormat','yyyy-MM-dd HH:mm:ss');
StopTime_datetime=datetime(StopTime_datestring,'InputFormat','yyyy-MM-dd HH:mm:ss');
sc.StartTime=StartTime_datetime
sc.StopTime=StopTime_datetime

But this code:

StartTime_datetime=datetime(StartTime_datestring,'Format','yyyy-MM-dd HH:mm:ss');
StopTime_datetime=datetime(StopTime_datestring,'Format','yyyy-MM-dd HH:mm:ss');
sc.StartTime=StartTime_datetime
sc.StopTime=StopTime_datetime