PROCEDURE: GET_MVN_EPH PURPOSE: Locates and reads MAVEN spacecraft ephemeris data. The result is packaged into a common block structure and returned. The available coordinate frames are: GEO = body-fixed Mars geographic coordinates (non-inertial) = IAU_MARS (sometimes called planetocentric (PC) coordinates) X -> 0 deg E longitude, 0 deg latitude Y -> 90 deg E longitude, 0 deg latitude Z -> 90 deg N latitude (= X x Y) origin = center of Mars units = kilometers MSO = Mars-Sun-Orbit coordinates (approx. inertial) X -> from center of Mars to center of Sun Y -> opposite to Mars' orbital angular velocity vector Z = X x Y origin = center of Mars units = kilometers USAGE: get_mvn_eph, trange, eph INPUTS: tvar: An array in any format accepted by time_double(). You explicitly input the specified time you want to get. eph: A named variable to hold the result. KEYWORDS: resolution: The time resolution with which you want to get the ephemeris data can be determined. silent: Minimizes the information shown in the terminal. make_array: Even if you do not use the "resolution" keyword, 10,000 elements structure array is automatically returned. status: Returns the calculation status: 0 = no data found 1 = partial data found 2 = complete data found CREATED BY: Takuya Hara on 2014-10-07. LAST MODIFICATION: $LastChangedBy: hara $ $LastChangedDate: 2014-11-26 11:42:32 -0800 (Wed, 26 Nov 2014) $ $LastChangedRevision: 16310 $ $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/maven/eph/get_mvn_eph.pro $ MODIFICATION LOG: (YYYY-MM-DD) 2014-10-07: Initial version. Usage is very limited. 2014-10-13: Enables to directly load SPICE/kernels information. 2014-10-21: Added "vss" keyword. It can restore the spacecraft velocity in the MSO coordinate system. But the data format has not been confirmed yet. It's just TBD now. 2014-11-24: No longer using IDL save files utilized by 'maven_orbit_tplot'. Hence, "sav", "date" and "extended" keywords are removed. Removed "vss" keyword. Information about spacecraft velocity is included in default. 2014-11-25: Header description is completely written up. Results are stored into common blocks.