[MOIMS-NAV-EXEC] Current Orbit Data Message (with new section 6 OCM) for your review/comment...
Oltrogge, Daniel
doltrogge at agi.com
Mon Jul 11 20:25:06 UTC 2016
David et al -
Here's what I've found (below) from the NASA planetary ephem modeling. As Dave Vallado and I have been reviewing more current research, it appears that the NASA approach is no longer a best practice for a number of reasons, not to mention the fact that the SPICE ephem have now mostly switched to a binary message (can CCSDS support binary as well? Just curious).
I've now inserted the (perhaps?) final component to the OCM section (section 6), which is a generic specification of what I'm calling Ephemeris Compression (EC) segments. This blends concepts from JPL, NASA/Houston, Hoots, and Vitali. With the addition of this final section (and after incorporating your feedback), we should be in a position to begin testing the message.
Comments/feedback welcomed.
Thanks,
Dan
Daniel L. Oltrogge
SDC Program Manager & Senior Research Astrodynamicist
Center for Space Standards and Innovation
Analytical Graphics Incorporated
Voice: 719-660-5142; E-mail: oltrogge at agi.com
-----Original Message-----
From: William Folkner [mailto:william.m.folkner at jpl.nasa.gov]
Sent: Tuesday, June 28, 2016 2:55 PM
To: Oltrogge, Daniel <doltrogge at agi.com>
Subject: Re: FW: FW: Planetary Ephemeris Chebyshev Ephemeris Representation (Intro)
Hi Dan,
For the JPL planetary ephemerides, we fit states (positions and velocities) for the planets, Sun, and Moon to Chebyshev polynomials using the method described in the attached paper. The French ephemeris group does the same, the Russian ephemeris group uses a slightly different formulation. There is a good writeup of the format of the files agreed to at
http://arxiv.org/abs/1507.04291
Basically we choose a time span (often 32 days, but 8 days for Moon), order of the polynomial, and use the position and velocity of each Cartesian component of the body at 8 equal time intervals (9 discrete times) to fit the Chebyshev polynomial coefficients. This method has continuous position and velocity across time boundaries, but not continuous acceleration. Our use has changed little over the past 30 years, so isn't something we think about much.
I am tied up this week and early next week, but could talk after that.
Regards,
Bill F.
On 6/27/16 7:41 AM, Oltrogge, Daniel wrote:
> Gents -
>
> I don't think we've met, but I'm supporting JPL in the CCSDS standards
> development initiatives as well as ISO space ops and orbital debris
> mitigation standards.
>
> I've been developing a standard for the exchange of orbital
> information called the Orbit Data Message, currently with three
> "subtypes" (Orbit Parameters Message, Orbit Ephemeris Message, and
> Orbit Mean element Message), and I'm working to add a 4th subtype
> called the Orbit Comprehensive Message (OCM).
>
> ESA asked me to add the ability to share orbit information via
> polynomials and/or other ephemeris compression techniques, and I'm
> struggling with the best way to do that.
>
> Since it looks like you folks work with Chebyshev representations of
> planetary ephemerides, I wonder if you'd be available to chat with me
> about that (or direct me to someone who can)?
>
> Thanks,
>
> Dan
>
> Daniel L. Oltrogge SDC Program Manager & Senior Research
> Astrodynamicist Center for Space Standards and Innovation Analytical
> Graphics Incorporated Voice: 719-660-5142; E-mail: oltrogge at agi.com
>
> -----Original Message----- From: Jon D. Giorgini
> [mailto:jdg at tycho.jpl.nasa.gov] Sent: Wednesday, June 22, 2016 1:16 PM
> To: Oltrogge, Daniel <doltrogge at agi.com> Subject: Re: FW:
> Planetary Ephemeris Chebyshev Ephemeris Representation (Intro)
>
> Dan,
>
> #1) I'm responsible for JPL comet/asteroid SPK files, which are
> created on demand through the publicly available Horizons ephemeris
> system:
>
> http://ssd.jpl.nasa.gov/?horizons_doc#spk (general
> description) telnet ssd.jpl.nasa.gov 6775a (interactive interface)
> http://ssd.jpl.nasa.gov/x/spk.html
> (browser interface) ftp://ssd.jpl.nasa.gov/pub/ssd/SCRIPTS/smb_spk
> (automation script)
>
> Small-body files are NOT produced with Chebyshev's since it is
> difficult to to reliably produce polynomial fits with acceptable
> accuracy across planetary close encounters.
>
> Small body files are instead produced using Type 1 or Type 21 SPK
> files (difference lines), which represent the internal integrator
> state exactly.
>
> #2) The JPL planetary ephemerides ARE represented with Chebyshev
> polynomials. SPK file/container versions are publicly available
> here:
>
> ftp://ssd.jpl.nasa.gov/pub/eph/planets/bsp/
>
> There is also an older planetary ephemeris format still used by
> some:
>
> ftp://ssd.jpl.nasa.gov/pub/eph/planets/fortran/ (software)
> ftp://ssd.jpl.nasa.gov/pub/eph/planets/ascii/ (data files)
>
> Note there was an effort under the IAU (International Astronomical
> Union) which standardized on the SPK container for planetary
> ephemerides, so that Russian and French ephemerides can also be
> represented in SPK files.
>
> The planetary files are produced by William.M.Folkner at jpl.nasa.gov If
> you need further information on them, contact him.
>
> #3) Natural satellite ephemerides often used Chebyshev storage file
> representation, but not always. Sometimes they are represented as
> dynamical models such as precessing ellipses or equinoctial elements.
> Whatever the representation, they can be distributed in SPK file
> containers, but may not be expressible in Chebyshev's with acceptable
> accuracy.
>
> The creator of natural satellite solution files is
> Robert.A.Jacobson at jpl.nasa.gov , who can provide more details if
> needed.
>
> Basically, ephemeris data produced at JPL is represented in a variety
> of different ways according to the nature of the problem. Thus the
> SPICE subsystem SPK approach of a library of readers that read/write
> whatever the appropriate native format is. We (JPL Solar System
> Dynamics) just create whichever representation is warranted for the
> problem and hand others "an SPK file". The details are then handled in
> software which supports almost two dozen representation methods.
>
> Internally at JPL, yet a different ephemeris container (not SPK) is
> used for optimal speed for flight operations, but this is not
> supported outside the lab, since it involves specialized and fairly
> obscure formats. (i.e. spacecraft ephemerides are produced in a
> different format which can be converted to SPK, though usually Type 1
> or Type 21 SPK, not Chebyshev because of the accuracy problems with
> polynomials).
>
> ----------------------------------------------------------------------
> ---------
>
>
Jon Giorgini | Navigation & Mission Design Section
> Senior Analyst | Solar System Dynamics Group
> Jon.Giorgini at jpl.nasa.gov | Jet Propulsion Laboratory
> ----------------------------------------------------------------------
> ---------
>
>
>> From doltrogge at agi.com Wed Jun 22 05:59:25 2016 From: "Oltrogge,
>> Daniel" <doltrogge at agi.com> To: "Jon.D.Giorgini at jpl.nasa.gov"
>> <Jon.D.Giorgini at jpl.nasa.gov> Subject: FW: Planetary Ephemeris
>> Chebyshev Ephemeris Representation (Intro) Date: Wed, 22 Jun 2016
>> 12:59:22 +0000
>>
>> Jon -
>>
>> I'm supporting development of international standards for space
>> operations and orbital debris mitigation. One of the standards we're
>> revising is the Orbit Data Message (ODM), a joint CCSDS and ISO
>> standard.
>>
>> I've been asked to include the ability for operators to share their
>> ephemerides by way of Chebyshev polynomials. I'm looking to contact
>> NASA folks who use such a representation to see what the format for
>> sharing their coefficients is.
>>
>> Do you have knowledge in such application (e.g. SPICE polys) or can
>> you forward me to someone who does?
>>
>> Thanks,
>>
>> Dan
>>
>> Daniel L. Oltrogge SDC Program Manager & Senior Research
>> Astrodynamicist Center for Space Standards and Innovation Analytical
>> Graphics Incorporated Voice: 719-660-5142; E-mail:
>> oltrogge at agi.com
>>
>> -----Original Message----- From: Berry, David S (3920)
>> [mailto:david.s.berry at jpl.nasa.gov] Sent: Friday, May 13, 2016 2:17
>> PM To: Oltrogge, Daniel <doltrogge at agi.com> Subject: Planetary
>> Ephemeris Chebyshev Ephemeris Representation (Intro)
>>
>>
>> Dan:
>>
>> This link is the user guide for the Horizons system, which is
>> provided by JPL's Solar System Dynamics group. There are a couple of
>> mentions of the Chebyshev polynomial representation in here.
>> There's also an email address for Jon Giorgini, who can probably
>> answer many of your questions.
>>
>> http://ssd.jpl.nasa.gov/?horizons_doc
>>
>> Also, the following documentation discusses the detailed format in a
>> SPICE file representation of the planetary ephemeris type 2 or type 3
>> (2 = Chebyshev positions, 3 = Chebyshev positions & velocity). Do a
>> find on "Cheby" to get the links to the detail.
>>
>> http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/spk.html
>>
>> This may help. Let me know...
>>
>> Regards, David
> .
>
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