Richard Paxman, ARKA Group; Thomas Rimmele, DKIST, National Solar Observatory; Andreas Hayden, ARKA Group
Keywords: cislunar SDA, adaptive optics, detection, tracking,
Abstract:
Richard G. Paxman, David A. Carrara
ARKA Group,
Thomas R. Rimmele
Director, DKIST
Abstract: Many ground-based and space-based telescopes are subject to solar and lunar exclusion zones, greatly constraining their use in cislunar Space-Domain Awareness (SDA). Such constraints create “cones of shame” in which satellites from adversaries can hide. The exclusion limitations for solar telescopes are dramatically reduced relative to conventional visible telescopes. We show that the 4-meter Daniel K. Inouye Solar Telescope (DKIST), located on Mt. Haleakala, can potentially be used to detect and track cislunar targets.
Historically, Space-Domain Awareness (SDA) has centered on detecting and tracking satellites and debris within the sphere circumscribing Geosynchronous Earth Orbit (GEO). However, in recent years there have been efforts by governments and private entities to establish a lunar presence. Some actors are proceeding without transparency, suggesting the need for SDA over a sphere encompassing the moon. Because the range to the moon is roughly 10 times of that to GEO orbit, the volume over which SDA is required is roughly times as large as has previously been needed. This is a challenging technical problem.
The problem of cislunar SDA is confounded by the fact that conventional earth-based and space-based telescopes are constrained by lunar- and solar-exclusion restrictions [1]. One approach to this problem is to design a large constellation of space telescopes for which some subset will not be subject to exclusion at any given time owing to the constellation design. This is an expensive proposition.
Solar telescopes have dramatically reduced exclusion restrictions. Indeed, they are designed to observe solar phenomena. We propose to investigate the use of solar telescopes as a ground-based adjunct to future space-based SDA constellations. Such telescopes have the advantage of being much easier to operate and maintain than space-based assets. In addition, the investment for solar telescopes has often already been made.
We investigate exercising the DKIST telescope for use in cislunar SDA. DKIST, located on Mt. Haleakala, is operated by the National Solar Observatory (NSO) and is a facility of the National Science Foundation (NSF). DKIST is the world’s largest solar telescope, with an off-axis design (no obscurations) and a 4-meter diameter primary mirror. DKIST also operates an Adaptive Optics (AO) system to achieve diffraction-limited imaging of solar phenomena [2].
We propose pathfinder experiments using DKIST to explore the efficacy of detecting, tracking, and retaining custody of cislunar (or more generally xGEO) satellites by using solar telescopes. We plan to use stars over a range of magnitudes as surrogates for xGEO satellites. The detection performance of DKIST can be quantified as a function of star magnitude, the amount of atmospheric turbulence and scattering, and the angular distance from the moon or the sun. Faint objects can be detected during dedicated and limited nights. Note that, unlike conventional telescopes, there is no lunar exclusion for the DKIST telescope. DKIST can also retain custody of xGEO satellites during the daytime. DKIST has substantially reduced solar exclusion restrictions relative to conventional telescopes.
Detection performance will be dramatically improved when using an AO capability. The DKIST telescope has already demonstrated an AO lock on the bright star Sirius during daylight hours. This proof-of-concept demonstration is encouraging, but we are confident that that AO can be used on fainter stars with various hardware modifications, including using wavefront sensing optimized for low photon flux. We explore such candidate upgrades. We report on detection SNR analyses for direct detection for satellites isolated in space. We have also evaluated detection SNR for occlusion detection for infrequent instances of solar and lunar transits.
References
[1] S.R. Knister, “Evaluation framework for cislunar space domain awareness (SDA) systems.”, MS Thesis (2020).
[2] T.R. Rimmele, et al., “The Daniel K. Inouye solar telescope–observatory overview.” Solar Physics 295 (2020).
Date of Conference: September 16-19, 2025
Track: SDA Systems & Instrumentation