The astorb database at Lowell Observatory

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Nicholas A. Moskovitza, Lawrence Wassermana, Brian Burta, Robert

Schottlanda, Edward Bowella, Mark Bailenb, Mikael Granvikc,d

aLowell Observatory, 1400 W Mars Hill Road, Flagstaﬀ, AZ 86001, USA

bUSGS Astrogeology, Flagstaﬀ, AZ

cDepartment of Physics, P.O. Box 64, 00014 University of Helsinki, Finland

dAsteroid Engineering Lab, Lule˚a University of Technology, Box 848, SE-981 28 Kiruna,

Sweden

Abstract

The astorb database at Lowell Observatory is an actively curated catalog

of all known asteroids in the Solar System. astorb has heritage dating back to

the 1970’s and has been publicly accessible since the 1990’s. Beginning in 2015

work began to modernize the underlying database infrastructure, operational

software, and associated web applications. That eﬀort has involved the expan-

sion of astorb to incorporate new data such as physical properties (e.g. albedo,

colors, spectral types) from a variety of sources. The data in astorb are used to

support a number of research tools hosted at https://asteroid.lowell.edu.

Here we present a full description of the software tools, computational founda-

tion, and data products upon which the astorb ecosystem has been built.

Keywords: Asteroids, Asteroids, dynamics

1. The history of astorb

Over the past 50 years the number of known minor planets in the Solar Sys-

tem has increased by 2.5 orders of magnitude from just under 4000 objects in

1970 to more than 1.2 million in 2022 (Figure 1). Maintaining catalogs of mi-

nor planets has required increasing eﬀort from the few organizations around the

world who curate these data. The discovery and designation of minor planets

∗Corresponding author

Email address: nmosko@lowell.edu (Nicholas A. Moskovitz)

Preprint submitted to Astronomy & Computing October 20, 2022

arXiv:2210.10217v1 [astro-ph.EP] 18 Oct 2022

begins with the accumulation of individual observations (e.g. right ascension,

declination, time, observatory location, apparent magnitude) at the Interna-

tional Astronomical Union’s Minor Planet Center (IAU MPC). These observa-

tions and their linkage to new or known minor planets are published by the MPC

for independent analysis. Heliocentric orbits (ecliptic reference plane, reference

epoch of J2000) deﬁned by orbital elements semi-major axis a, eccentricity e,

inclination i, argument of perihelion ω, longitude of the ascending node Ω, and

mean anomaly Mfor each minor planet are determined by ﬁtting these ob-

servations (Section 2). Following similar ﬁtting processes, catalogs of orbital

elements are curated at the MPC, by the Solar System Dynamics group at JPL,

in Italy by a consortium that began at the University of Pisa, and by Lowell

Observatory in Flagstaﬀ, Arizona.

Figure 1: Histogram of ﬁrst observation dates for all asteroids in astorb as of 25 July 2021.

The dramatic growth in the number of known minor planets will continue as next generation

surveys like the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST) begin in

the mid 2020’s (Jones et al., 2009).

Lowell’s astorb catalog of asteroid orbits has grown organically into a mod-

ern relational database and associated web infrastructure. However, the origins

of astorb trace back to the 1970’s when Lowell astronomer Ted Bowell main-

tained a catalog of asteroid orbits on IBM punch cards which were input to

an IBM 1130 computer1. These orbit cards were manually created by Bowell

based on monthly circulars issued by the MPC. Orbits were also calculated for

objects that were discovered “in house” and then passed on to Brian Marsden,

director of the MPC at the time. The software infrastructure used to process

these orbits was developed by Lowell astronomer Lawrence Wasserman.

A primary driver for maintaining this stack of punch card orbits was to have

the ability to compute ephemerides for all known asteroids (a process described

in Section 2). These ephemeris predictions were used to ﬁnd known asteroids

on both recent and historic photographic plates, and later ﬁlm exposures. At

the time, many numbered asteroids were on the verge of being lost if new as-

trometry was not provided. Asteroids are generally numbered after observations

have been obtained across four oppositions (though exceptions requiring fewer

oppositions have been made for objects such as near-Earth asteroids). This was

not the case for some objects. Work at Lowell focused on trying to solve this

problem, which necessitated maintaining this local catalog of minor planet or-

bits. These early orbit computations were performed one object at a time and

took about 5 minutes per object to complete on the IBM 1130. The full catalog

contained fewer than 10,000 objects until 1980, and thus could be maintained

in this manner with regular processing of the few hundred objects each month

that needed to be updated.

1This computer had been installed at Lowell on 6 November 1966, seven years prior to

Ted Bowell’s arrival at the Observatory. From the Lowell Observatory annual report for 1966,

the IBM 1130 computer was “equipped with 8 K core memory, disk pack, card reader, paper

tape reader, and line printer. [It] was installed in November 1966 in the soundproof, air-

conditioned computer room of the Observatory’s Planetary Research Center”. This center

along with the computer were funded by a NASA grant to facilitate studies related to the

analysis of planetary imagery.

Starting around 1977, use of the astorb catalog was paired with the ongo-

ing Palomar Planet Crossing Asteroid Survey (PCAS) led by Gene Shoemaker,

Carolyn Shoemaker, and Eleanor Helin. PCAS was carried out at the Palomar

0.46m Schmidt with a primary objective of discovering near-Earth asteroids

(Helin and Shoemaker, 1979). The PCAS ﬁlms were developed soon after expo-

sure and Bowell would get phone calls when objects with high rates of motion

(consistent with a near Earth orbit) were discovered. Follow-up observations at

Lowell would focus on conﬁrmation and sometimes characterization including

measurement of photometric phase curves, colors, and lightcurves. This process

was quite eﬃcient, such that orbits and physical characteristics were determined

for new objects often before announcement of discovery had been made by the

MPC.

In the mid 1980’s the maintenance of this orbit catalog was made easier

with the installation of a VAX 11/750 super minicomputer (about the size of

a large washing machine). Integrations for individual objects would now only

take a few seconds, and on board storage meant that the catalog could be saved

to disk. This deprecated the use of punch cards and made astorb a digital

catalog, though it wouldn’t be given that name until the next decade.

In the early 1990’s Bowell and Finnish astronomer Karri Muinonen explored

the mathematical problem of assessing orbit uncertainty and the associated error

in positional (ephemeris) prediction (e.g. Muinonen and Bowell, 1993; Muinonen

et al., 1994). This work led to the realization that an orbit database in the public

domain that contained information beyond that published by the MPC would

be of value to the research community (Bowell et al., 1993, 1994). By 1994,

a ﬂat ASCII ﬁle called astorb.dat containing orbits for 22,725 asteroids and

updated daily was available for download from Lowell’s anonymous ftp site2.

Though the format of this ﬁle has changed over the years, the basic information

has remained constant and includes designations, absolute magnitudes, physical

2astorb.dat continues to be hosted and available for download at https://ftp.lowell.

edu/pub/elgb/astorb.dat

properties (slope parameter G,B−Vcolor, IRAS diameter and taxonomy), orbit

details, and several parameters related to predicted ephemeris uncertainties.

Two years after astorb became downloadable, the VizieR library of astro-

nomical catalogs maintained at the Centre de Donn´ees astronomiques de Stras-

bourg (CDS) started hosting the ASCII catalog of orbits3. This was the ﬁrst

ever live catalog served by VizieR. It continues to be updated weekly and re-

mains a valuable resource that sees ∼500 −1000 requests per month through

VizieR alone.

The combined VizieR and Lowell access points to the astorb catalog helped

to build a broad base of users. In the research community this is evidenced

by regular citations dating back to the original public release (e.g. Morbidelli,

1996). In addition, the SkyBot minor planet identiﬁcation tool (Berthier et al.,

2006) was developed based on the orbits in astorb and has since been lever-

aged by the Gaia mission (Gaia Collaboration et al., 2016) to identify known

asteroids in Gaia ﬁelds (Carry et al., 2021). Commercial software packages that

directly ingest the astorb data ﬁle include Starry Night, The Sky, and Sky

Safari. This capability has helped astorb maintain relevance to the hobbyist

and amateur astronomy communities. As a whole, users of the astorb system

include professional and unpaid professional astronomers, educators and stu-

dents, and general public who are scientiﬁcally curious. Given this user base,

we have undertaken a major development eﬀort to modernize the entirety of the

astorb system so that it is easier to maintain and will be able to accommodate

ongoing growth of the minor planet catalog (Figure 1).

2. Orbit Fitting and Integration

Two key operations that support astorb involve ﬁtting orbits to sets of

observations and the integration of orbits to various epochs. The basic methods

involved in these process are well established (e.g. Gauss, 1809), but we describe

3https://cdsarc.cds.unistra.fr/viz-bin/cat/B/astorb

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TheastorbdatabaseatLowellObservatoryNicholasA.Moskovitza,LawrenceWassermana,BrianBurta,RobertSchottlanda,EdwardBowella,MarkBailenb,MikaelGranvikc,daLowellObservatory,1400WMarsHillRoad,Flagsta,AZ86001,USAbUSGSAstrogeology,Flagsta,AZcDepartmentofPhysics,P.O.Box64,00014UniversityofHelsinki,FinlanddAs...

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The astorb database at Lowell Observatory

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