Pan-STARRS Document Control PSDC-500-001-00

______Pan-STARRS Project Management System

Orbit Determination & Software Summary

Jim Heasley & Robert Jedicke Pan-STARRS Moving Object Processing Systems Group Institute for Astronomy 15 April 2004

© Institute for Astronomy, University of Hawaii 2680 Woodlawn Drive, Honolulu, Hawaii 96822 An Equal Opportunity/Affirmative Action Institution Pan-STARRS Document Control PSDC-500-001-00

Revision History

Revision Date Affected Explanation of Change Pages 00 15 April 2004 placed under PSDC

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Table of Contents

Revision History ...... 2 Table of Contents...... 3 1 Executive Summary...... 4 2 Introduction...... 4 3 Software Packages...... 5 3.1 Orbfit...... 5 3.2 ORSA...... 6 3.3 FindOrb...... 6 3.4 CODES ...... 8 3.5 Lowell Ephemeris...... 8 3.6 JPL Ephemeris Service (Horizons)...... 9 3.7 Minor Center (MPC)...... 9 3.8 Tholen Routines...... 10 4 Recommendations...... 11

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Orbit Determination & Ephemeris Software Summary

1 Executive Summary

PanSTARRS requires preliminary (or short-arc) orbit determination software (various modes of Gauss, Vaisala, and circular ), perturbative orbit determination software (initial and updating) with error determination and ephemeris generating software (with sky-plane error determination).

Unfortunately, none of the publicly available orbit determination and ephemeris generating software packages satisfies all of PanSTARRS’s needs. Most can easily be excluded from consideration because they are unavailable, untested or unwieldy. The most likely candidates for PanSTARRS usage in order of decreasing utility in the opinion of the authors are OrbFit and Dave Tholen’s routines. A combination of the strengths of each might be a good starting point.

The advantage of OrbFit is that it is a well respected and much used standard in asteroid and orbit determination and ephemeris generation software implemented on the AstDys website. The advantage of Tholen’s routines is that they are already maintained and supported by a dependable member of the PanSTARRS team.

2 Introduction

PanSTARRS requires orbit determination and ephemeris generating software within the Moving Object (MO) pipeline and for offline analysis of MO data. Chesley has outlined the functionality of the MO pipeline in http://pan-starrs.ifa.hawaii.edu/project/workshops/dp_04_01_03/talks/ jedicke_neo_talk.pdf or .ppt. The orbit determination and ephemeris generating software is a relatively small (he estimated about 20%) component of the envisioned pipeline. It could be re-generated in-house but if publicly available software packages are sufficient for PanSTARRS’s purposes it would be economical to use them. At the very least it is prudent to survey what is currently available. This document summarizes the orbit determination and ephemeris generating software packages of which we are aware:

Orbfit ORSA FindOrb CODES Lowell Observatory Asteroid Ephemeris JPL Ephemeris Service (Horizons) Center (MPC) Tholen Routines

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In Section 3 we provide (when available) the following information for each package when available:

Package name Author(s) Website License/Availability Programming Language Current Version Level of Documentation Support Other Comments

3 Software Packages

3.1 Orbfit

Package name: OrbFit

Author(s): Andreas Milani ([email protected]) & OrbFit Consortium

Website: http://newton.dm.unipi.it/orbfit/

License/Availability: Open source style arrangement

Programming Language: Fortran 77

Current Version: 2.3.3

Level of Documentation: The source code is reasonably well commented so the purpose of most subroutines is clear. Some other small amounts of documentation are available. It is possible, but not easy to learn how to use the program using the available information.

Support: The website invites requests for support but in my experience there has been no response to such requests or bug reports.

Other: OrbFit is the software used to support the NEODys and AstDys data available on the Asteroid Services website at http://newton.dm.unipi.it. In one-on-one tests with the JPL ephemeris software the computed ephemerides are virtually indistinguishable.

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The software built easily "out of the box." The Solaris version did *not* operate properly, presumably due to a compiler incompatibility. A working code on Solaris was created using the gcc compiler and some modifications to the Makefile parmameters.

The next release of OrbFit is advertised to be in Fortran 90.

3.2 ORSA

Package name: Orbit Reconstruction, Simulation, and Analysis (ORSA)

Author(s): Pasquale Tricarico ([email protected]) and others

Website: http://orsa.sourceforge.net

License/Availability: GPL Open Source

Programming Language: C++

Current Version: 0.30

Level of Documentation: Virtually no useful documentation

Support: Unknown

Other: The package compiled properly after some work in terms of installing other software it requires. It does appear to execute under linux but with no documentation it is very difficult to assess whether it works as advertised.

It purports to have or plan to implement much of the same level of analysis that OrbFit has, e.g., covariance matrices, collision predicting, etc.

3.3 FindOrb

Package name: Find Orb

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Author(s): Bill Gray, Project [email protected])

Website: http://www.projectpluto.com

License/Availability: Open source freely available for non- commercial use (DOS/Linux version only)

Programming Language: C++

Current Version: Unknown, constantly under revision

Level of Documentation: Source code is documented at some level. The web site gives some insights into the working of the program.

Support: Bill Gray has been responsive to requests for help although he only seems interested in incorporating new features that are of interest to him.

Other: FindOrb comes in two flavors: a Windows version and a DOS (or linux) version. The latter has been tested on a single case against the same set of input (synthetic) observations as OrbFit. The derived were very similar and the forward projected ephemeris (6 in time) were very close (order of an arcsecond). This is very interesting in that this simple code generally uses "fits" to the orbits of the major rather than the JPL ephemeris (although it can do so).

Gray has taken some rather simple minded approaches to implementing methods described in some of the standard celestial textbooks. However, it would appear the proof is in the pudding -- at least in some cases this rather basic implementation works as nicely as OrbFit. It does not, however, have the analytical error analysis capability of the latter. Gray does seem to take the lead of some of the other packages, like OrbFit, and has implemented Monte Carlo error analysis.

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Package name: Comet/asteroid Orbit Determination and Ephemeris Software (CODES)

Author(s): Jim Baer ([email protected])

Website: http://users.stargate.net/~jimbaer/index.html

License/Availability: Source available

Programming Language: Java

Current Version: 3.1

Level of Documentation: Web page fairly complete

Support: unknown

Other: This package is a GUI based orbit determination and analysis system. It claims to have much of the sort of sophisticated analysis found in OrbFit. This package has not yet been tested.

3.5 Lowell Observatory Asteroid Ephemeris

Package name: Lowell Observatory Asteroid Ephemeris (ASTEPH)

Author(s): Ted Bowell, Bruce Koehn

Website: http://asteroid.lowell.edu

License/Availability: Proprietary, availability unknown. Bowell has in the past indicated that his code was freely available.

Programming Language: Unknown

Current Version: 1.5

Level of Documentation: Unknown

Support: My one "complaint" about its performance (it would only compute an ephemeris on full hour times) was acknowledged and I was told this couldn't be fixed.

Other: This appears to be an ephemeris generation tool only, with no provisions for orbit

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determination from observations. It is well known that Bowell has orbit determination software available as well – his group produces the well respected and widely used astorb database of asteroid and comet orbital elements (ftp://ftp.lowell.edu/pub/elgb/astorb.html).

3.6 JPL Ephemeris Service (Horizons)

Package name: JPL Ephemeris Service (Horizons)

Author(s): JPL Solar Systems Dyanmics group

Website: http://ssd.jpl.nasa.gov/horizons.html

License/Availability: Proprietary, availability unknown

Programming Language: Unknown

Current Version: Unknown

Level of Documentation: Application documentation is excellent

Support: JPL team has been responsive to requests

Other: This package defines the "gold standard" in ephemeris calculations. There does not appear to be any publicly available orbit determination software.

3.7 (MPC)

Package name: MPC Software

Author(s): Brian G. Marsden (MPC) and others

Website: http://cfa-www.harvard.edu/iau/mpc.html

License/Availability: Proprietary

Programming Language: Fortran / VMS

Current Version: Unknown

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Level of Documentation: Unknown

Support: N/A


3.8 Tholen Routines

Package name(s): SEARCH – creates a list of objects appearing in a FOV EPHEM - Generates 2-body moving object ephemeredes. Commercially available for the PC. KNOBS(2)-short arc probabilistic orbit and ephemeris generation DTPGM - ephemeris package provided to 2MASS PERT - non-linear perturbative orbit determination PERT-AUTO - non-linear perturbative orbit determination with automatic outlier rejection ORBIT403e – guassian and differential orbit determination

Author(s): David Tholen (IfA) & JPL

Website: N/A

License/Availability: Available for PanSTARRS use with minimal restrictions.

Programming Language: Fortran 77 (some Fortran 90)

Current Version: Updated as necessary. Versioning by date.

Level of Documentation: Core library routines have excellent documentation. In publicly distributed software the source code documentation is also excellent and there exists extensive on-line help. Other routines that call the library routines are generally very well documented.

Support: Tholen is an IfA Faculty member and on the PanSTARRS team at the 10-20% FTE level. He would be willing to provide support for implementing existing code and time to improve aspects of the code which are not yet optimized.

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Other: Dave’s software is extremely well documented and characteristically well-tested. 2-body ephemeris generation code provides positions consistent with other standards (JPL, OrbFit, MPC) but his code does not yet integrate orbits to the time of observation.

Perturbative orbit solutions are non-linear and are therefore on the order of 1000X slower than the linear perturbative solutions implemented at the major orbit determination sites (JPL, AstDys, MPC). The linear method could be implemented.

These routines cannot yet make use of range observations. Dave says he could make the modifications but has not yet had the need to do so.

The tremendous advantage to using Tholen’s software is the fact that he is on-site and a PanSTARRS team member. Problems with the code could be dealt with swiftly.

4 Recommendations

We recommend that PanSTARRS members interested in orbit determination and ephemeris generation software begin using and testing the OrbFit software and developing wrappers for that package to make it easier to use. This effort has already been started by Heasley and Jedicke and Kaiser.

We also recommend that PanSTARRS explore the use of David Tholen’s routines. In particular, we need to discuss the possibility that he agree to provide PanSTARRS with improved (faster, linearized) perturbative orbit solution software with full error determination capability. We should encourage Dave to provide a series of well-documented canned sub-routines tailored to PanSTARRS needs as he has already done for 2MASS.