Abstract
Abstract. Radar observations can be used to obtain accurate orbital elements for near-Earth objects (NEOs) as a result of the very accurate range and range rate measureables. These observations allow the prediction of NEO orbits further into the future and also provide more information about the properties of the NEO population. This study evaluates the observability of NEOs with the EISCAT 3D 233 MHz 5 MW high-power, large-aperture radar, which is currently under construction. Three different populations are considered, namely NEOs passing by the Earth with a size distribution extrapolated from fireball statistics, catalogued NEOs detected with ground-based optical telescopes and temporarily captured NEOs, i.e. mini-moons. Two types of observation schemes are evaluated, namely the serendipitous discovery of unknown NEOs passing the radar beam and the post-discovery tracking of NEOs using a priori orbital elements. The results indicate that 60–1200 objects per year, with diameters D>0.01 m, can be discovered. Assuming the current NEO discovery rate, approximately 20 objects per year can be tracked post-discovery near the closest approach to Earth. Only a marginally smaller number of tracking opportunities are also possible for the existing EISCAT ultra-high frequency (UHF) system. The mini-moon study, which used a theoretical population model, orbital propagation, and a model for radar scanning, indicates that approximately seven objects per year can be discovered using 8 %–16 % of the total radar time. If all mini-moons had known orbits, approximately 80–160 objects per year could be tracked using a priori orbital elements. The results of this study indicate that it is feasible to perform routine NEO post-discovery tracking observations using both the existing EISCAT UHF radar and the upcoming EISCAT 3D radar. Most detectable objects are within 1 lunar distance (LD) of the radar. Such observations would complement the capabilities of the more powerful planetary radars that typically observe objects further away from Earth. It is also plausible that EISCAT 3D could be used as a novel type of an instrument for NEO discovery, assuming that a sufficiently large amount of radar time can be used. This could be achieved, for example by time-sharing with ionospheric and space-debris-observing modes.
Highlights
All current radar observations of near-Earth objects (NEOs), namely asteroids and comets with perihelion distance q < 1.3 au, are conducted post-discovery (Ostro, 1992; Taylor et al, 2019)
The amount of radar observations of NEOs is limited by resources, i.e. there are significantly more observing opportunities during close approaches than there is radar time available on the Arecibo (2.36 GHz, 900 kW) and Goldstone DSS-14 (8.56 GHz, 450 kW) radars, which are the two radars that perform most of the tracking of asteroids on a routine
In order to increase the number of radar measurements of NEOs, it is desirable to extend routine NEO observations to smaller radars, such as the existing EISCAT radars or the upcoming EISCAT 3D radar (233 MHz, 5 MW), abbreviated to E3D, which is to be located in FennoScandinavian Arctic
Summary
All current radar observations of near-Earth objects (NEOs), namely asteroids and comets with perihelion distance q < 1.3 au, are conducted post-discovery (Ostro, 1992; Taylor et al, 2019). In order to increase the number of radar measurements of NEOs, it is desirable to extend routine NEO observations to smaller radars, such as the existing EISCAT radars or the upcoming EISCAT 3D radar (233 MHz, 5 MW), abbreviated to E3D, which is to be located in FennoScandinavian Arctic. While these radars may not be capable of observing objects nearly as far away as Arecibo or Goldstone or generating high-quality range–Doppler images, these radars are able to produce high-quality ranging
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