From aannex1 at jhu.edu Sat Jul 9 18:46:45 2022 From: aannex1 at jhu.edu (Andrew Annex) Date: Sun, 10 Jul 2022 01:46:45 +0000 Subject: [Spice_discussion] SpiceyPy 5.1.0 is now available. Message-ID: Hello fellow guild navigators! SpiceyPy 5.1.0 has been released and is now available on PyPI. It will likely be available on the conda-forge within the next few hours. This release adds a majority of new functions from CSPICE N67 to SpiceyPy. A list of the new functions that were added is included in the change log. The change log is available in the GitHub repository and also at https://urldefense.us/v3/__https://spiceypy.readthedocs.io/en/main/changelog.html__;!!PvBDto6Hs4WbVuu7!YDENo4MNVEtTsWBu51tdR4nlFeU11K3mp4CwLLY1zGqWcmXJoms2YGOpl3SXyihoXo7iS33tTTyEzg$ . As a reminder, SpiceyPy was peer-reviewed and published by The Journal of Open Source Software (JOSS). Please remember to cite SpiceyPy in your work using the doi: https://urldefense.us/v3/__https://doi.org/10.21105/joss.02050__;!!PvBDto6Hs4WbVuu7!YDENo4MNVEtTsWBu51tdR4nlFeU11K3mp4CwLLY1zGqWcmXJoms2YGOpl3SXyihoXo7iS30zQcmjgQ$ as well as the NAIF directly, following their instructions. [https://urldefense.us/v3/__https://joss.theoj.org/logo_large.jpg__;!!PvBDto6Hs4WbVuu7!YDENo4MNVEtTsWBu51tdR4nlFeU11K3mp4CwLLY1zGqWcmXJoms2YGOpl3SXyihoXo7iS32eBvAuog$ ] SpiceyPy: a Pythonic Wrapper for the SPICE Toolkit Annex et al., (2020). SpiceyPy: a Pythonic Wrapper for the SPICE Toolkit. Journal of Open Source Software, 5(46), 2050, https://urldefense.us/v3/__https://doi.org/10.21105/joss.02050__;!!PvBDto6Hs4WbVuu7!YDENo4MNVEtTsWBu51tdR4nlFeU11K3mp4CwLLY1zGqWcmXJoms2YGOpl3SXyihoXo7iS30zQcmjgQ$ doi.org thanks for reading! -- Dr. Andrew Annex. California Institute of Technology, GPS JHU Earth & Planetary Science https://urldefense.us/v3/__http://www.andrewannex.com__;!!PvBDto6Hs4WbVuu7!YDENo4MNVEtTsWBu51tdR4nlFeU11K3mp4CwLLY1zGqWcmXJoms2YGOpl3SXyihoXo7iS30vF_dbfQ$ -------------- next part -------------- An HTML attachment was scrubbed... URL: From troy.d.goodson at jpl.nasa.gov Wed Jul 13 12:23:55 2022 From: troy.d.goodson at jpl.nasa.gov (Goodson, Troy D (US 392C)) Date: Wed, 13 Jul 2022 19:23:55 +0000 Subject: [Spice_discussion] how are the long-term predicts made for ITRF93? Message-ID: <084C5435-163E-41D5-A5A7-66AF4B13A1B9@JPL.NASA.gov> The tutorial https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Tutorials/pdf/individual_docs/23_lunar-earth_pck-fk.pdf as well as https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/aareadme.txt describe long-term predicts for ITRF93: Low accuracy, long term predict kernel. The extended predict region of this kernel---the time interval following the end of the predict region of the input EOP file---does not estimate changes in UT1-TAI. The dates in the file name are the file's coverage start and stop times: earth_200101_990628_predict.bpc But, I believe IERS only provides predicts for 1 year. See https://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html and EOP2 files from https://eop2-external.jpl.nasa.gov are only predicted for about 78 days. What is the source for the long-term prediction in a BPC kernel like earth_200101_990628_predict.bpc? Thanks, Troy. -------------- next part -------------- An HTML attachment was scrubbed... URL: From nathaniel.j.bachman at jpl.nasa.gov Wed Jul 13 13:49:03 2022 From: nathaniel.j.bachman at jpl.nasa.gov (Bachman, Nathaniel J (US 392N)) Date: Wed, 13 Jul 2022 20:49:03 +0000 Subject: [Spice_discussion] how are the long-term predicts made for ITRF93? In-Reply-To: References: Message-ID: <083f72d665c94bb2b00b199d2442f9b3@jpl.nasa.gov> Hi Troy, Here's the complete comment section of the file earth_200101_990628_predict.bpc >>> Low accuracy, long term predict earth PCK ========================================= Original file name: earth_200101_990628_predict.bpc Creation date: 2020 April 11 18:17:00 PDT Created by: Nat Bachman (JPL/NAIF) Data Sources Input file: extended EOP created from JPL EOP file latest.long (Copied from WWW URL http://epic.jpl.nasa.gov/nav/eop/latest.long) Source EOP metadata: $ JPL Earth Orientation Parameter File $ Last Data Point 6-APR-2020 $ Predicts to 28-JUN-2020 $ EOPLBL='EOP. LAST DATUM 6-APR-2020. PREDICTS->28-JUN-2020, UT1TYP=UT1. ' EOPFNG='Enter MAKE_EOP 6-Apr-2020 11:04:43 linked 12-Jan-2017 00:15:37 ' EOPUT1='UT1' EOPTYP='EOP' EOPTIM=' 6-Apr-2020 11:04:43 ' EOPTRF='ITRF93' EOPCRF='ICRF93' Input file: leapseconds kernel naif0012.tls Coverage Start time: 2020 JAN 01 00:01:09.183 TDB Stop time: 2099 JUN 28 00:01:09.182 TDB UTC Epoch of last datum: 6-APR-2020 Particulars This is low-accuracy predict PCK file giving the orientation of the Earth as a function of time for the interval shown above. This PCK file is made from an extended EOP file which consists of the JPL EOP file named above, with four extra records appended. These records are designed to add 79 years to the coverage of the EOP file without affecting interpolated data values for times within the coverage interval of the original EOP file. Data values of records in the extended interval are constant, with the exception of the TAI-UT1 offsets. Those are adjusted so that the corresponding values of TAI-UT1R are constant. The terrestrial frame whose orientation is given by this file is ITRF93; the inertial base frame is Ecliptic of J2000. Rotational effects included are: -Precession (1976 IAU model) -Nutation (1980 IAU model) -Nutation corrections -Rotation through true sidereal time -Polar motion -Nutation corrections Euler angles have been extracted from the Ecliptic-to-ITRF93 rotation matrix, and Chebyshev polynomials were fit to the Euler angles. The Chebyshev expansion degree was 49; the degree of the retained polynomials is 20. The coverage interval for each set of polynomials is 1 day or less. This file represents the same earth orientation as does the input EOP file for the time range: 01-JAN-2020 UTC 28-JUN-2020 UTC For epochs after the end of EOP coverage, polar motion and nutation corrections from the EOP file are held constant at values obtained by extrapolating 1 day from the last source EOP record. TAI-UT1 values are set so that the corresponding TAI-UT1R values at each epoch of the extrapolated records are equal. Details of the EOP extrapolation process are given below. Let n be the number of data records in the original EOP file. Let MJD(i) be the epoch of the ith record expressed as a modified Julian date. The added records have the following characteristics: Record n+1: Epoch is MJD(n) + 1. Nutation correction and polar motion values are obtained by extrapolating to the epoch a cubic Lagrange interpolating polynomial fitted to the corresponding data in records n-3 : n. TAI-UT1 is obtained by converting to TAI-UT1R the TAI-UT1 data in records n-3 : n, extrapolating an interpolating polynomial as for the other data, then converting the extrapolated TAI-UTR1 value to TAI-UT1. UTC string is consistent with the MJD epoch. Record n+2: Epoch is MJD(n) + 2. Nutation correction and polar motion values match those of record n+1. TAI-UT1 is set so that the corresponding value of TAI-UT1R at this epoch is that corresponding to TAI-UT1 at the epoch of record n+1. UTC string is consistent with the MJD epoch. Record n+3: Epoch is MJD(n) + 3. Data values are as described for record n+2, adjusted for this epoch. Record n+4: Epoch is MJD(n) + 28854. Data values are as described for record n+2, adjusted for this epoch. In all of the four records described above, the values of TAI-UT1 have been selected so the corresponding values of TAI-UT1R are constant and equal to the value resulting from extrapolating the cubic interpolating polynomial for TAI-UT1R, fitted to the final four values of TAI-UT1R derived from the original EOP file, to the epoch of record n+1. The expected behavior of the interpolation algorithm is as follows: Time range Interpolation characteristics ============ ============================= Epoch of record 1 to epoch of record n-1: Interpolation is identical to standard EOP file. Orientation error relative to that provided by a binary PCK derived from the source EOP file is non-zero due to differences in the Chebyshev fitting process. Error is at the 1.1 nanoradian level. Epoch of record n-1 to epoch of record n: Nearly identical to standard EOP file; small round-off error will occur. Orientation error is at the 1.1 nanoradian level. Epoch of record n to epoch of record n+1: Some ringing of interpolated data will occur. This interval has duration 1 day. Orientation error relative to that provided by a binary PCK derived from a JPL EOP released 4 days after the source JPL EOP file (thereby providing accurate predicted data 4 days further into the future--up to 2020 July 2) is at the 225 nanoradian level. Epoch of record n+1 to epoch of record n+2: Some ringing of interpolated data will occur. This interval has duration 1 day. Orientation error measured as for the interval described above is at the 245 nanoradian level. Epoch of record n+2 to epoch of record n+3: Ideally nutation corrections and polar motion will be constant, as will TAI-UT1R derived from TAI-UT1 values in the file. Some round-off error should be expected. This interval has duration 1 day. Orientation error measured as for the interval described above is at the 265 nanoradian level. Epoch of record n+3 to epoch of record n+4: Data are as described for records n+2 to n+3. This interval has duration 79 years. Orientation difference relative to the IAU_EARTH reference frame's rotation model ranges from the 1.25 milliradian level at the interval start to the 4.75 milliradian level at the end. >>> So, as you see, the only data source is the cited JPL EOP file. Since TAI-UT1 is frozen at the end of the EOP coverage interval, the orientation from the PCK for times after that epoch will be off by, on average, about 1 arcsecond for each future leapsecond. Nutation and polar motion will be off too, but the magnitudes of those errors are dominated by that of the spin error. This file enables operation of applications that require Earth binary PCKs having very long coverage, but that require only very low accuracy. For example, using this file, view periods can be computed with an accuracy of a few minutes. Please let me know if you have further questions. Best regards, -Nat Bachman (JPL/NAIF) Nathaniel.Bachman at jpl.nasa.gov ________________________________________ From: Spice_discussion on behalf of Goodson, Troy D (US 392C) Sent: Wednesday, July 13, 2022 12:23 PM To: spice_discussion at naif.jpl.nasa.gov Subject: [Spice_discussion] how are the long-term predicts made for ITRF93? The tutorial https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Tutorials/pdf/individual_docs/23_lunar-earth_pck-fk.pdf as well as https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/aareadme.txt describe long-term predicts for ITRF93: Low accuracy, long term predict kernel. The extended predict region of this kernel---the time interval following the end of the predict region of the input EOP file---does not estimate changes in UT1-TAI. The dates in the file name are the file's coverage start and stop times: earth_200101_990628_predict.bpc But, I believe IERS only provides predicts for 1 year. See https://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html and EOP2 files from https://eop2-external.jpl.nasa.gov are only predicted for about 78 days. What is the source for the long-term prediction in a BPC kernel like earth_200101_990628_predict.bpc? Thanks, Troy. -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: ATT00001.txt URL: From troy.d.goodson at jpl.nasa.gov Wed Jul 13 15:51:34 2022 From: troy.d.goodson at jpl.nasa.gov (Goodson, Troy D (US 392C)) Date: Wed, 13 Jul 2022 22:51:34 +0000 Subject: [Spice_discussion] how are the long-term predicts made for ITRF93? In-Reply-To: <083f72d665c94bb2b00b199d2442f9b3@jpl.nasa.gov> References: <083f72d665c94bb2b00b199d2442f9b3@jpl.nasa.gov> Message-ID: <1438550C-96F1-47A3-8BAB-46C9B81A1A64@JPL.NASA.gov> Nat, Thank you. That's the information I was looking for. I should've thought to get the comment section with "commnt -r earth_200101_990628_predict.bpc" :/ Troy. https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/ug/commnt.html > On Jul 13, 2022, at 1:49 PM, Bachman, Nathaniel J (US 392N) wrote: > > > Hi Troy, > > Here's the complete comment section of the file > > earth_200101_990628_predict.bpc > >>>> > > Low accuracy, long term predict earth PCK > ========================================= > > Original file name: earth_200101_990628_predict.bpc > Creation date: 2020 April 11 18:17:00 PDT > Created by: Nat Bachman (JPL/NAIF) > > Data Sources > > Input file: extended EOP created from > > JPL EOP file latest.long > (Copied from WWW URL > http://epic.jpl.nasa.gov/nav/eop/latest.long) > > Source EOP metadata: > > $ JPL Earth Orientation Parameter File > $ Last Data Point 6-APR-2020 > $ Predicts to 28-JUN-2020 > $ > EOPLBL='EOP. LAST DATUM 6-APR-2020. PREDICTS->28-JUN-2020, UT1TYP=UT1. ' > EOPFNG='Enter MAKE_EOP 6-Apr-2020 11:04:43 linked 12-Jan-2017 00:15:37 ' > EOPUT1='UT1' > EOPTYP='EOP' > EOPTIM=' 6-Apr-2020 11:04:43 ' > EOPTRF='ITRF93' > EOPCRF='ICRF93' > > Input file: leapseconds kernel naif0012.tls > > > Coverage > > Start time: 2020 JAN 01 00:01:09.183 TDB > Stop time: 2099 JUN 28 00:01:09.182 TDB > > UTC Epoch of last datum: 6-APR-2020 > > Particulars > > This is low-accuracy predict PCK file giving the orientation of the Earth as > a function of time for the interval shown above. This PCK file is made from > an extended EOP file which consists of the JPL EOP file named above, with > four extra records appended. These records are designed to add 79 years to > the coverage of the EOP file without affecting interpolated data values for > times within the coverage interval of the original EOP file. Data values > of records in the extended interval are constant, with the exception of > the TAI-UT1 offsets. Those are adjusted so that the corresponding values > of TAI-UT1R are constant. > > The terrestrial frame whose orientation is given by this file is ITRF93; the > inertial base frame is Ecliptic of J2000. Rotational effects included are: > > -Precession (1976 IAU model) > -Nutation (1980 IAU model) > -Nutation corrections > -Rotation through true sidereal time > -Polar motion > -Nutation corrections > > Euler angles have been extracted from the Ecliptic-to-ITRF93 rotation matrix, > and Chebyshev polynomials were fit to the Euler angles. The Chebyshev > expansion degree was 49; the degree of the retained polynomials is 20. > The coverage interval for each set of polynomials is 1 day or less. > > This file represents the same earth orientation as does the input EOP file > for the time range: > > 01-JAN-2020 UTC > 28-JUN-2020 UTC > > For epochs after the end of EOP coverage, polar motion and nutation > corrections from the EOP file are held constant at values obtained by > extrapolating 1 day from the last source EOP record. TAI-UT1 values are > set so that the corresponding TAI-UT1R values at each epoch of the > extrapolated records are equal. Details of the EOP extrapolation process > are given below. > > Let n be the number of data records in the original EOP file. Let > MJD(i) be the epoch of the ith record expressed as a modified > Julian date. The added records have the following > characteristics: > > Record n+1: Epoch is MJD(n) + 1. Nutation correction and polar > motion values are obtained by extrapolating to the > epoch a cubic Lagrange interpolating polynomial > fitted to the corresponding data in records n-3 : n. > TAI-UT1 is obtained by converting to TAI-UT1R the > TAI-UT1 data in records n-3 : n, extrapolating an > interpolating polynomial as for the other data, then > converting the extrapolated TAI-UTR1 value to TAI-UT1. > UTC string is consistent with the MJD epoch. > > Record n+2: Epoch is MJD(n) + 2. Nutation correction and polar > motion values match those of record n+1. TAI-UT1 is > set so that the corresponding value of TAI-UT1R at > this epoch is that corresponding to TAI-UT1 at the > epoch of record n+1. UTC string is consistent with the > MJD epoch. > > Record n+3: Epoch is MJD(n) + 3. Data values are as described for > record n+2, adjusted for this epoch. > > Record n+4: Epoch is MJD(n) + 28854. Data values are as described > for record n+2, adjusted for this epoch. > > In all of the four records described above, the values of TAI-UT1 > have been selected so the corresponding values of TAI-UT1R are > constant and equal to the value resulting from extrapolating the cubic > interpolating polynomial for TAI-UT1R, fitted to the final four values > of TAI-UT1R derived from the original EOP file, to the epoch of > record n+1. > > The expected behavior of the interpolation algorithm is as follows: > > Time range Interpolation characteristics > ============ ============================= > > Epoch of record 1 to > epoch of record n-1: Interpolation is identical to standard EOP > file. > > Orientation error relative to that provided > by a binary PCK derived from the source EOP > file is non-zero due to differences in the > Chebyshev fitting process. Error is at the > 1.1 nanoradian level. > > Epoch of record n-1 to > epoch of record n: Nearly identical to standard EOP file; > small round-off error will occur. > > Orientation error is at the 1.1 nanoradian > level. > > Epoch of record n to > epoch of record n+1: Some ringing of interpolated data > will occur. This interval has duration 1 day. > > Orientation error relative to that provided > by a binary PCK derived from a JPL EOP > released 4 days after the source JPL EOP file > (thereby providing accurate predicted data > 4 days further into the future--up to 2020 > July 2) is at the 225 nanoradian level. > > Epoch of record n+1 to > epoch of record n+2: Some ringing of interpolated data will occur. > This interval has duration 1 day. > > Orientation error measured as for the > interval described above is at the > 245 nanoradian level. > > Epoch of record n+2 to > epoch of record n+3: Ideally nutation corrections and polar > motion will be constant, as will TAI-UT1R > derived from TAI-UT1 values in the file. > Some round-off error should be expected. > This interval has duration 1 day. > > Orientation error measured as for the > interval described above is at the > 265 nanoradian level. > > Epoch of record n+3 to > epoch of record n+4: Data are as described for records n+2 to > n+3. This interval has duration 79 years. > > Orientation difference relative to the > IAU_EARTH reference frame's rotation model > ranges from the 1.25 milliradian level at > the interval start to the 4.75 milliradian > level at the end. > >>>> > > So, as you see, the only data source is the cited JPL EOP file. > > Since TAI-UT1 is frozen at the end of the EOP coverage interval, the orientation > from the PCK for times after that epoch will be off by, on average, about 1 arcsecond for > each future leapsecond. Nutation and polar motion will be off too, but the magnitudes > of those errors are dominated by that of the spin error. > > This file enables operation of applications that require Earth binary PCKs > having very long coverage, but that require only very low accuracy. For example, > using this file, view periods can be computed with an accuracy of a few minutes. > > Please let me know if you have further questions. > > Best regards, > > -Nat Bachman (JPL/NAIF) > > Nathaniel.Bachman at jpl.nasa.gov > > > > > ________________________________________ > From: Spice_discussion on behalf of Goodson, Troy D (US 392C) > Sent: Wednesday, July 13, 2022 12:23 PM > To: spice_discussion at naif.jpl.nasa.gov > Subject: [Spice_discussion] how are the long-term predicts made for ITRF93? > > The tutorial https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/Tutorials/pdf/individual_docs/23_lunar-earth_pck-fk.pdf > as well as https://naif.jpl.nasa.gov/pub/naif/generic_kernels/pck/aareadme.txt > describe long-term predicts for ITRF93: > > Low accuracy, long term predict kernel. The extended predict region of this > kernel---the time interval following the end of the predict region of the > input EOP file---does not estimate changes in UT1-TAI. The dates in the > file name are the file's coverage start and stop times: > > earth_200101_990628_predict.bpc > > > But, I believe IERS only provides predicts for 1 year. See https://www.iers.org/IERS/EN/DataProducts/EarthOrientationData/eop.html > and EOP2 files from https://eop2-external.jpl.nasa.gov are only predicted for about 78 days. > > What is the source for the long-term prediction in a BPC kernel like earth_200101_990628_predict.bpc? > > Thanks, > > Troy. > _______________________________________________ > Spice_discussion mailing list > Spice_discussion at naif.jpl.nasa.gov > http://naif.jpl.nasa.gov/mailman/listinfo/spice_discussion