PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Information on MESSENGER Light Time Files." PUBLICATION_DATE = 2015-10-09 END_OBJECT = TEXT END MESSENGER Science Data Archive Radio Science Subsystem LTFINFO.TXT 15 June 2015 Johns Hopkins University Applied Physics Laboratory ============================================================================= INTRODUCTION ============================================================================= The ancillary/ltf directory contains MESSENGER Light Time Files (LTF). These files provide one way light travel time values for both the upleg and downleg directions between the MESSENGER spacecraft and the three Deep Space Communications Complex (DSCC) facilities. This product was produced by the navigation team every month or so during mission operations and on selected intervals from improved reconstructed ephemeris. The data are in table form. See the LTF SIS (document/ltf_sis.htm) for a detailed description of this product. These are accompanied by detached full PDS labels. LTF files follow the following naming convention where the first is the year and day of year of the beginning of the period covered by the particular product file and the second is the year and day of year of the end of the period covered by the particular product file. ltf/mess_rs___ltf.tab ============================================================================= ORIGINAL LTF PRODUCTS ============================================================================= These LTFs were generated based on the original ephemeris products produced by the mission that include both initial reconstructed and predicted ephemeris. They are associated with "orbit determinations" and cover the duration of the mission. These orbit determination (od) LTFs are the original LTF products for use with the radio science data. These are the only archived LTF products produced after orbital insertion through to the end of the mission. ============================================================================= CRUISE PHASE RECONSTRUCTED LTF PRODUCTS ============================================================================= In addition to the original orbit determination LTFs provided during the cruise phases of the mission (i.e., shortly after launch up to right before Mercury orbital insertion, including planetary flybys), there are LTF products produced from an improved, reconstructed ephemeris that became available later. These reconstructed ephemeris LTFs or "recon LTFs" provide slightly better accuracy than the original ephemeris LTFs provided for the pre-orbit period. The recon LTFs supersede the original LTFs covering the pre-orbit period; however the original LFT files remain in the archive because they are sufficiently accurate for radio science purposes and the periods covered by each file align with the original ephemeris products. The slightly more accurate "recon LTFs" are provided in the event that they might be useful. The files do not cover the same periods as each original LTF, but cumulatively cover the whole pre-orbit period. The recon LTFs use the same file naming convention as the original LTFs. One may distinguish them based upon the ORIGINAL_PRODUCT_ID field in their associated labels. The original LTFs, which each accompanied a revised trajectory or new "orbit determination," have "_od" followed by a three-digit orbit determination number as part of their original operations filename preserved in the ORIGINAL_PRODUCT_ID field. The recon LTFs have the string "recon" followed by a combination of letters and numbers in their original operations file names. For example: From an example original LTF label: ORIGINAL_PRODUCT_ID = "msgr_sowlt_20150429_20150430_od431.txt" From an example recon LTF label: ORIGINAL_PRODUCT_ID = "msgr_sowlt_20090601_20090701_recon006b.txt" The recon LTF products provided in this archive are also listed below. mess_rs_2004216_2004245_ltf mess_rs_2004244_2004275_ltf mess_rs_2004274_2004306_ltf mess_rs_2004305_2004336_ltf mess_rs_2004335_2005001_ltf mess_rs_2004366_2005032_ltf mess_rs_2005031_2005060_ltf mess_rs_2005059_2005091_ltf mess_rs_2005090_2005121_ltf mess_rs_2005120_2005152_ltf mess_rs_2005151_2005182_ltf mess_rs_2005181_2005213_ltf mess_rs_2005212_2005244_ltf mess_rs_2005243_2005274_ltf mess_rs_2005273_2005305_ltf mess_rs_2005304_2005335_ltf mess_rs_2005334_2006001_ltf mess_rs_2005365_2006032_ltf mess_rs_2006031_2006060_ltf mess_rs_2006059_2006091_ltf mess_rs_2006090_2006121_ltf mess_rs_2006120_2006152_ltf mess_rs_2006151_2006182_ltf mess_rs_2006181_2006213_ltf mess_rs_2006212_2006244_ltf mess_rs_2006243_2006274_ltf mess_rs_2006273_2006305_ltf mess_rs_2006304_2006328_ltf mess_rs_2006328_2006335_ltf mess_rs_2006334_2007001_ltf mess_rs_2006365_2007032_ltf mess_rs_2007031_2007060_ltf mess_rs_2007059_2007091_ltf mess_rs_2007090_2007121_ltf mess_rs_2007120_2007152_ltf mess_rs_2007151_2007182_ltf mess_rs_2007181_2007186_ltf mess_rs_2007186_2007213_ltf mess_rs_2007212_2007244_ltf mess_rs_2007243_2007274_ltf mess_rs_2007273_2007305_ltf mess_rs_2007304_2007335_ltf mess_rs_2007334_2008001_ltf mess_rs_2007365_2008014_ltf mess_rs_2008013_2008016_ltf mess_rs_2008015_2008032_ltf mess_rs_2008031_2008046_ltf mess_rs_2008046_2008061_ltf mess_rs_2008060_2008092_ltf mess_rs_2008091_2008122_ltf mess_rs_2008121_2008153_ltf mess_rs_2008152_2008183_ltf mess_rs_2008182_2008214_ltf mess_rs_2008213_2008245_ltf mess_rs_2008244_2008250_ltf mess_rs_2008250_2008280_ltf mess_rs_2008279_2008311_ltf mess_rs_2008311_2008336_ltf mess_rs_2008335_2009001_ltf mess_rs_2008366_2009032_ltf mess_rs_2009031_2009060_ltf mess_rs_2009059_2009091_ltf mess_rs_2009090_2009121_ltf mess_rs_2009120_2009152_ltf mess_rs_2009151_2009182_ltf mess_rs_2009181_2009213_ltf mess_rs_2009212_2009240_ltf mess_rs_2009240_2009244_ltf mess_rs_2009243_2009274_ltf mess_rs_2009272_2009273_ltf mess_rs_2009273_2009303_ltf mess_rs_2009303_2009343_ltf mess_rs_2009303_2010001_ltf mess_rs_2009343_2010060_ltf mess_rs_2010001_2010060_ltf mess_rs_2010060_2010121_ltf mess_rs_2010060_2010125_ltf mess_rs_2010121_2010176_ltf mess_rs_2010125_2010256_ltf mess_rs_2010176_2010244_ltf mess_rs_2010244_2010305_ltf mess_rs_2010256_2010331_ltf mess_rs_2010305_2011001_ltf mess_rs_2010331_2011040_ltf mess_rs_2011040_2011070_ltf mess_rs_2011070_2011076_ltf mess_rs_2011076_2011082_ltf NOTE: mess_rs_2011076_2011082_ltf covers the orbital insertion period and is the only LTF for that interval.