Rank: 134 based on 620 downloads (last 30 days) and 21 files submitted
photo

Darin Koblick

E-mail
Company/University
California State University and Claremont Graduate University
Lat/Long
33.8078, -118.3698

Personal Profile:
Professional Interests:
Astrodynamics

 

Watch this Author's files

 

Files Posted by Darin View all
Updated   File Tags Downloads
(last 30 days)
Comments Rating
12 Dec 2013 Screenshot Convert Keplerian Orbital Elements to a State Vector Convert orbital elements to a state vector, or a state vector back to orbital elements. Author: Darin Koblick keplerian, orbital elements, aerospace, conversion, position, velocity 62 1
  • 5.0
5.0 | 1 rating
18 Apr 2013 Screenshot Vectorized Solar Azimuth and Elevation Estimation Predict the topocentric solar position defined by geodetic lat, lon, Alt, and a universal time Author: Darin Koblick aerospace, alt, altitude, astronomy, az, azimuth 40 3
  • 4.0
4.0 | 3 ratings
26 Feb 2013 Screenshot 2000 ASTM Standard Extraterrestrial Spectrum Reference E-490-00 Vectorized MATLAB code which will compute the solar flux given a wave length. Author: Darin Koblick solar flux, astm, solar spectrum, blackbody, flux 12 0
14 Dec 2012 Screenshot Vectorized Clohessy-Wiltshire Hill Linear Propagation A Demonstration of Linear Satellite Orbit Propagation Using Clohessy-Wiltshire Equations of Motion. Author: Darin Koblick linear propagation, chw, clohessy, wiltshire, linear, propagation 29 0
  • 5.0
5.0 | 2 ratings
23 Jul 2012 Flatten Any Mulitdimensional Matrix into a 2-D Matrix! Convert any multidimensional matrix into a 2-D Matrix. Then convert it back to its original form. Author: Darin Koblick matrix, 2d, flattening, multidimensional, multidim 17 0
Comments and Ratings by Darin View all
Updated File Comments Rating
01 Sep 2013 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick

Chad,

The two code lines you are referencing are trying to find the midnight that occurs before the provided Julian Date.

As written, the first check will be true if the Julian date occurs after midnight and 12+ hours before the time.

As written, the second check will be true if the Julian date occurs after midnight and less than 12 hours before the time.

If both checks are true, the code will use the last midnight that occurred. This is the desired functionality.

Because I am rounding down on the Julian date and subtracting a half day, there is no possible way that jd could be less than jdMin.

-Darin

20 Oct 2012 Convert UTC to Solar Apparent Time Convert a time given in UTC to Solar Apparent or Solar Mean Time Author: Darin Koblick

Brandon,

Also, if you are trying to compare the Solar Apparent Time, (SAT) be sure to input the longitude in degrees (W < 0, E > 0).

You can see that this function will match the solutions (almost exactly ... depending on the year) to those solutions in Example 4 of the ASTRONOMICAL INFORMATION SHEET No. 58 http://astro.ukho.gov.uk/nao/services/ais58.pdf

20 Oct 2012 Convert UTC to Solar Apparent Time Convert a time given in UTC to Solar Apparent or Solar Mean Time Author: Darin Koblick

Brandon,

Latitude and Longitude are needed to determine the input time value to the equation of time (UT). They aren't needed to determine the equation of time ... it has nothing to do with latitude and longitude. Perhaps you should compare to a location with a 0hr local time offset.

See this document for a description of what the equation of time is, you can also compare results to this as an "example". I don't guarantee any specific accuracy with EoT as it depends on the mean anomaly of the sun which is obviously a first/second order approximation.

http://www.ips.gov.au/Educational/2/1/14

11 Aug 2012 Convert ECEF to ECI Coordinates Take any vector or series of vectors in the ECEF Coordinate frame and convert them to ECI. Author: Darin Koblick

John,

35 leap seconds since 1972 sounds like that is indeed what you are seeing in STK. As you know, ECEFtoECI.m takes in a Julian date, so the correction would not be internal to this particular conversion routine.

In fact, I don't think Mathworks attempts to address this issue with their juliandate.m routine. You would more than likely want to make the leap second correction when converting UTC to Julian date.

Are you able to check for the estimated position differences using Julian date in STK instead of UTC? Perhaps this should make the comparisons a little more accurate as well.

Truthfully, unless you are trying to use this routine in high-precision satellite mission operations, as long as you are consistent with your coordinate frame conversions (i.e. always using these conversion routines), it really shouldn't matter if there are minor discrepancies with STK (it is all relative motion anyway).

-Darin

28 Jun 2012 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick

Drake,

J2000 is factored into the ECI to ECEF conversion routine through the call to JD2GAST.m (converts Julian Date to Greenwhich Apparent Sidereal Time). In order to do this, the effects of nutation are considered, and depend on the correct number of Julian centuries since J2000.

Comments and Ratings on Darin's Files View all
Updated File Comment by Comments Rating
05 Dec 2013 Vectorized Clohessy-Wiltshire Hill Linear Propagation A Demonstration of Linear Satellite Orbit Propagation Using Clohessy-Wiltshire Equations of Motion. Author: Darin Koblick Son, juyoung

01 Sep 2013 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick Koblick, Darin

Chad,

The two code lines you are referencing are trying to find the midnight that occurs before the provided Julian Date.

As written, the first check will be true if the Julian date occurs after midnight and 12+ hours before the time.

As written, the second check will be true if the Julian date occurs after midnight and less than 12 hours before the time.

If both checks are true, the code will use the last midnight that occurred. This is the desired functionality.

Because I am rounding down on the Julian date and subtracting a half day, there is no possible way that jd could be less than jdMin.

-Darin

29 Aug 2013 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick Hawes, Chad

29 Aug 2013 Convert ECI to ECEF Coordinates Transform ECI position, velocity and acceleration to ECEF position, velocity & acceleration. Author: Darin Koblick Hawes, Chad

Darin,
In your JD2GMST function, I have a question related to the following two lines:

jd0(jd>jdMin) = jdMin(jd>jdMin);
jd0(jd>jdMax) = jdMax(jd>jdMax);

This appears to be limiting the Julian day between a lower bound and an upper bound. Don't you want the first line to be:

jd0(jd<jdMin) = jdMin(jd<jdMin);

Otherwise, it would appear that no actual lower bounding occurs...

Chad

31 Jul 2013 Vectorized Picard-Chebyshev Method Vectorized Picard-Chebyshev Method used for the analysis of the 2012 ASME Conference paper 87878 Author: Darin Koblick Binz, Chris

Contact us