marstimelocal
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Contents: Description, Arguments, Usage, Examples, Sub-Functions, Related Functions, Source Supported Under Version: > 1.13
Description Displays information regarding time at a user-specified location on Mars
Arguments and Return Values Parameters: A structure returned from marstimeglobal, and the planetocentric longitude and latitude of the desired site Return Value: Structure giving the parameters for local Mars time at the specified site
Usage Syntax: marstimelocal((global structure), longitude, latitude) For input, this function takes a structure returned from marstimeglobal, and the planetocentric longitude and latitude of the site for which to calculate the local time. Longitude is east positive; latitude is north positive. Most of the equations used in the Mars time calculations are adapted from NASA GISS Mars24 (available at http://www.giss.nasa.gov/tools/mars24/) and Allison, M., and M. McEwen (2000), A post-Pathfinder evaluation of aerocentric solar coordinates with improved timing recipes for Mars seasonal/diurnal climate studies, Planet. Space Sci., 48, 215-235, doi:10.1016/S0032-0633(99)00092-6 (available at http://pubs.giss.nasa.gov/cgi-bin/abstract.cgi?id=al05000n). The accuracy of the outputs depends on the accuracy of the inputs, including the time input to marstimeglobal. The accuracy limits listed below are for the best possible case, where the input location's coordinates are known exactly. NOTE that for the calculated time quantities, due to 0.004 degrees of uncertainty (1 part in 90,000) in the inertial location of the martian prime meridian, there is an uncertainty of 1 second (2.7e-4 hr, or 1.1e-5 sol) in all of these quantities, in addition to the theoretical limits given below. The function will return a structure with the local Mars time parameters for the input time and location. They are: Dt: J2000 TT offset, in days (this is just from the first input) lon: Planetocentric longitude, in degrees (second input); as accurate as input lat: Planetocentric latitude, in degrees (third input); as accurate as input lonpg: Planetographic longitude (west positive), in degrees; as accurate as input longitude latpg: Planetographic latitude, in degrees; accurate within ~0.01 degrees timezone: String specifying local time zone offset, relative to MTC. Martian time zones are simply defined to be 15 degrees wide, centered on every multiple of 15 degrees longitude. LMZT: Local Mean Zonal Time (analagous to local standard time on Earth), in hours; accurate within 0.1 sec (0.000028 hr) LMST: Local Mean Solar Time, in hours; accurate within 0.1 sec (0.000028 hr), provided the input longitude is accurate within well under 0.00042 degrees. LTST: Local True Solar Time, in hours; accurate within 3 s (0.000833 hr). Z: Local zenith (solar incidence angle); accurate to 0.15 degrees. The zenith equals zero if the Sun is directly overhead; it equals ninety degrees if the Sun is on the horizon. A: Local solar azimuth; accurate within ~0.05 degrees. The azimuth as defined here runs clockwise from north. The stated accuracy ranges are only applicable between 1900 and 2100. Outside that range, the returned values should be considered to be questionable. Most values in the returned structure are single precision (float format), since the values cannot be determined to enough significant figures to warrant double precision. When marstimelocal() is entered without any arguments, it prints its description, as shown below.
Examples dv> marstimelocal() Returns local Mars time data, given array of global Mars time data and planetocentric coordinates (east longitude positive) marstimelocal((global structure), longitude, latitude) global structure is a structure obtained from marstimeglobal NOTE that due to 0.004 degrees of uncertainty (1 part in 90,000) in the inertial location of the martian prime meridian, there is an uncertainty of 1 second in all of these quantities, in addition to the theoretical limits given below. Fields in returned structure (all angles in degrees): Dt: J2000 TT offset, in days (first input); as accurate as input lon: Planetocentric longitude (second input); as accurate as input lat: Planetocentric latitude (third input); as accurate as input lonpg: Planetographic longitude; as accurate as input longitude latpg: Planetographic latitude; accurate within ~0.01 degrees timezone: String specifying local time zone offset, relative to MTC Martian time zones are simply defined to be 15 degrees wide, centered on every multiple of 15 degrees longitude LMZT: Local Mean Zonal Time (local standard time), in hours; accurate within 0.1 sec (0.000028 hr) LMST: Local Mean Solar Time, in hours; accurate within 0.1 sec (0.000028 hr), provided the input longitude is accurate within well under 0.00042 degrees LTST: Local True Solar Time, in hours; accurate within 3 s (0.000833 hr) Z: Local zenith (solar incidence angle); accurate to 0.15 degrees A: Local solar azimuth; accurate within ~0.05 degrees All stated accuracies are for dates between 1900 and 2100, provided the input time is exact. Outside that range, questionable accuracy. See http://www.giss.nasa.gov/tools/mars24/help/algorithm.html and http://pubs.giss.nasa.gov/cgi-bin/abstract.cgi?doi=10.1016/ S0032-0633(99)00092-6 S. Marshall 11-10-2009 dv> ans = marstimeglobal(atod("3616.56492959585")) struct, 15 elements Dt: 3616.56492959585 M: 114.542068481445 aFMS: 5.60519933700562 PBS: -0.00852344091981649 EoC: 9.23740196228027 nu: 123.779472351074 R: 1.59311711788177 hlon: 99.8689727783203 hlat: 1.36212968826294 LS: 14.8426008224487 EoT: -0.525308728218079 MSD: 48311.4206288116 MTC: 10.0950918197632 ssplon: 36.4532585144043 decl: 6.26008462905884 dv> marstimelocal(ans, atod("175.4785"), atod("-14.7542")) # MER-A (Spirit) landing site struct, 11 elements Dt: 3616.56492959585 lon: 175.478500366211 lat: -14.7541999816895 lonpg: 184.521500000000 latpg: -14.9217443466187 timezone: "+12" LMZT: 22.0950927734375 LMST: 21.7936592102051 LTST: 21.2683506011963 Z: 138.893905639648 A: 262.619415283203 dv> marstimelocal(ans, atod("354.4742"), atod("-1.9483")) # MER-B (Opportunity) landing site struct, 11 elements Dt: 3616.56492959585 lon: 354.474212646484 lat: -1.94830000400543 lonpg: 5.52580000000000 latpg: -1.97143328189850 timezone: "+0" LMZT: 10.0950927734375 LMST: 9.72670650482178 LTST: 9.20139694213867 Z: 42.7249603271484 A: 78.4894790649414 |
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Recent Library Changes Created On: 11-18-2009 |
