Asteroid Photometry with PIRATE: Optimizations and Techniques for Small Aperture Telescopes

Abstract

Small aperture telescopes provide the opportunity to conduct high frequency, targeted observations of near-Earth Asteroids that are not feasible with larger facilities due to highly competitive time allocation requirements. Observations of asteroids with these types of facilities often focus on rotational brightness variations rather than longer-term phase angle-dependent variations (phase curves) due to the difficulty of achieving high precision photometric calibration. We have developed an automated asteroid light curve extraction and calibration pipeline for images of moving objects from the 0.43 m Physics Innovations Robotic Telescope Explorer. This allows for the frequency and quality of observations required to construct asteroid phase curves. Optimizations in standard data reduction procedures are identified that may allow for similar small aperture facilities, constructed from commercially available/off-the-shelf components, to improve the image and subsequent data quality. A demonstration of the hardware and software capabilities is expressed through observation statistics from a 10 months observing campaign, and through the photometric characterization of near-Earth Asteroids 8014 (1990 MF) and 19764 (2000 NF5).

The effect of aspect changes on Near-Earth Asteroid phase curves

“…As an example of the significance of this additional uncertainty, we present updated uncertainties for the two example phase curves from Jackson et al (2021a). In that work, the authors report the uncertainties for (8014) 1990 MF as 𝜎 𝐻 = 0.047 mag and 𝜎 𝐺 = 0.024.…”

“…Doing so results in a thermally derived geometric albedo, 𝑝 𝑉 = 0.270±0.080. Jackson et al (2021a) derived a phase curve for this asteroid, and so the input distributions of 𝐻 and 𝐺 were defined using the measured parameters as the means, and the statistical fit uncertainties used as the standard deviations (second line of Table 4). This analysis gives a geometric albedo 𝑝 𝑉 = 0.211 ± 0.021, within the uncertainty range of the values derived using the WISE-assumed phase curve parameters.…”

“…Section 5 details software code designed to estimate the aspect-related uncertainty in individual asteroid phase curves based on the geometry over which the asteroids were observed. As an example of the significance of this additional uncertainty, we use this software to present updated uncertainties for the phase curve parameters of the near-Earth Asteroids (8014) 1990 MF and (19764) 2000 NF5 originally observed and derived by Jackson et al (2021a). In Section 6, we report on the implications that this effect may have on studies across various wavelength ranges, such as thermophysical modelling.…”

“…Various NEATM fits to WISE W3 and W4 data for NEA (19764) 2000 NF5. Initial fit performed using assumed 𝐻 and 𝐺 parameters and uncertainties as used byMainzer et al (2011), second fit using derived phase curve parameters fromJackson et al (2021a), and the third fit using the same parameters but with aspect uncertainty added in quadrature to the statistical fit uncertainties.…”

Pre-impact Thermophysical Properties and the Yarkovsky Effect of NASA DART Target (65803) Didymos

“…In this study, we sought to confirm and refine the H V and G V values because our subsequent thermophysical modeling requires the Bond albedo to be derived in the V band. To supplement the Kitazato et al (2004) photometry, we collected additional V-band photometric measurements of Didymos before the DART impact with the OU PIRATE telescope (Kolb et al 2018;Jackson et al 2021).…”