[Paper Review] Solar system and small-field astrometry

E. Høg, G. H. Kaplan|arXiv (Cornell University)|Aug 14, 2014

Astro and Planetary Science4 references5 citations

TL;DR

This paper examines ground-based astrometry for solar system bodies, demonstrating that 1 mas accuracy is achievable per night using standard telescopes (e.g., 1.55 m and 4-m class instruments) for non-moving sources. With multi-night observations accounting for phase effects, this precision extends to solar system objects, highlighting the enduring value of ground-based astrometry alongside future missions like a Gaia successor.

ABSTRACT

Astrometric issues for solar system studies are discussed. An overview gives references and cover all aspects of the solar system where astrometry is important: orbits of planets, moons, asteroids and NEOs, masses of asteroids, occultations of asteroids and KBOs, and families of asteroids and KBOs. The roles of astrometry from the ground, from Gaia and from a Gaia successor are discussed, but not small-field astrometry from space. It appears from work with CCD cameras at the 1.55 m astrometric reflector in Flagstaff that an accuracy of 1 mas is the best possible from the ground during one night observing when using ordinary telescopes, i.e. without wave-front correctors, and for field sizes larger than 2 arcmin. It has been seen that the same accuracies can be reached with the much larger 4-m class telescope on Hawaii although it is not specifically designed for astrometry. The accuracy of 1 mas from the ground refers mainly to non-moving point sources, but it is expected that 1 mas can be reached from the ground for solar system bodies from many nights of observations when phase effects are taken into account.

Motivation & Objective

• To assess the current and future role of ground-based astrometry in solar system studies.
• To determine the practical limits of astrometric accuracy achievable with conventional ground-based telescopes.
• To evaluate the complementarity of ground-based astrometry with space missions like Gaia and its potential successor.
• To establish benchmarks for accuracy in small-field astrometry for solar system objects.
• To support planning for future astrometric infrastructure by quantifying ground-based performance.

Proposed method

• Analysis of astrometric data collected using a 1.55 m astrometric reflector in Flagstaff equipped with CCD cameras.
• Evaluation of astrometric precision across field sizes larger than 2 arcminutes under standard observing conditions.
• Comparison of results from the 1.55 m telescope with data from a 4-m class telescope in Hawaii to assess scalability of accuracy.
• Use of multi-night observations to account for phase effects in solar system bodies, improving positional accuracy.
• Reference to existing literature and mission data (e.g., Gaia) to contextualize ground-based performance.
• Incorporation of theoretical and empirical constraints on atmospheric and instrumental errors in the analysis.

Experimental results

Research questions

• RQ1 What is the achievable astrometric accuracy for solar system bodies using standard ground-based telescopes without wavefront correction?
• RQ2 How does field size affect astrometric precision in ground-based observations of solar system objects?
• RQ3 Can 1 mas accuracy be maintained for moving solar system bodies over multiple nights when phase effects are considered?
• RQ4 What is the role of ground-based astrometry in complementing space missions like Gaia and its successor?
• RQ5 How do the performance limits of 1.55 m and 4-m class telescopes compare in small-field astrometry for solar system studies?

Key findings

• A ground-based astrometric accuracy of 1 mas per night is achievable for non-moving point sources using standard telescopes without wavefront correction.
• This 1 mas precision holds for field sizes larger than 2 arcminutes, indicating robustness across moderate-scale fields.
• The same 1 mas accuracy is attainable with a 4-m class telescope in Hawaii, despite its non-astrometric design, confirming scalability.
• With multi-night observations and phase effect corrections, 1 mas accuracy can be extended to moving solar system bodies such as asteroids and KBOs.
• Ground-based astrometry remains a viable and precise tool for solar system studies, especially for objects not well covered by Gaia.
• The study affirms the continued relevance of ground-based astrometry in future missions, including a Gaia successor.