Fast solar radiation pressure modelling with ray tracing and multiple reflections

Abstract

Physics based SRP (Solar Radiation Pressure) models using ray tracing methods are powerful tools when modelling the forces on complex real world space vehicles. Currently high resolution (1 mm) ray tracing with secondary intersections is done on high performance computers at UCL (University College London). This study introduces the BVH (Bounding Volume Hierarchy) into the ray tracing approach for physics based SRP modelling and makes it possible to run high resolution analysis on personal computers. The ray tracer is both general and efficient enough to cope with the complex shape of satellites and multiple reflections (three or more, with no upper limit). In this study, the traditional ray tracing technique is introduced in the first place and then the BVH is integrated into the ray tracing. Four aspects of the ray tracer were tested for investigating the performance including runtime, accuracy, the effects of multiple reflections and the effects of pixel array resolution.Test results in runtime on GPS IIR and Galileo IOV (In Orbit Validation) satellites show that the BVH can make the force model computation 30-50 times faster. The ray tracer has an absolute accuracy of several nanonewtons by comparing the test results for spheres and planes with the analytical computations. The multiple reflection effects are investigated both in the intersection number and acceleration on GPS IIR, Galileo IOV and Sentinel-1 spacecraft. Considering the number of intersections, the 3rd reflection can capture 99.12%, 99.14%, and 91.34% of the total reflections for GPS IIR, Galileo IOV satellite bus and the Sentinel-1 spacecraft respectively. In terms of the multiple reflection effects on the acceleration, the secondary reflection effect for Galileo IOV satellite and Sentinel-1 can reach 0.2 nm/s 2 and 0.4 nm/s 2 respectively. The error percentage in the accelerations magnitude results show that the 3rd reflection should be considered in order to make it less than 0.035%. The pixel array resolution tests show that the dimensions of the components have to be considered when choosing the spacing of the pixel in order not to miss some components of the satellite in ray tracing. This paper presents the first systematic and quantitative study of the secondary and higher order intersection effects. It shows conclusively the effect is non-negligible for certain classes of misson.

Toward the 1-cm Galileo orbits: challenges in modeling of perturbing forces

“…1 Sun-satellite-Earth reference frame illustrating the angular elevation of the Sun above the orbital plane (β), the argument of latitude of the satellite with respect to the argument of latitude of the Sun (Δu), and the elongation angle . The X , Y , and Z directions are consistent with IGS (Montenbruck et al 2015b) be handled threefold (Ziebart 2004): using empirical orbit models such as an Empirical CODE Orbit Model (ECOM2, Arnold et al 2015), analytical models, e.g., using ray-tracing technique (Li et al 2018) or hybrid models such as an a priori cuboid model proposed by Montenbruck et al (2015a).…”

“…The analytical approach can be applied with the adaptation of solely physical properties of the satellites using, for instance, the ray-tracing technique (Li et al 2018) or in a hybrid way, with the additional estimation of the empirical parameters. Physical properties allow for the composition of the 'box-wing' model which simplifies spacecraft to the satellite bus ('box') and solar panels ('wing').…”

Copernicus Sentinel-1 satellites: sensitivity of antenna offset estimation to orbit and observation modelling

“…The yand z-component of the antenna offsets are estimated in all solutions and the corresponding a priori values are the differences between the main GPS ARP and COM coordinates (see bottom rows of Table 1). It is also common to all solutions that CNES-CLS (Loyer et al, 2012) Final orbit and clock products are used for the processing instead of the IGS Final orbit and clock products. Single-receiver ambiguity-fixing is done for solutions A-F based on the available widelane satellite biases from CNES-CLS together with corresponding GPS satellite clocks having included the narrowlane phase biases (Laurichesse et al, 2009).…”

“…Sophisticated satellite models based on ray tracing considering shadowing effects and multiple reflections proved to be beneficial to satellite macromodels (Haines et al, 2004;Zelensky et al, 2010) for the non-gravitational force modelling. Such a sophisticated Sentinel-1 satellite model has been developed by University College London (UCL, Li et al, 2018), but it is not publicly available and has not yet been validated in S1 POD. Therefore, self-shadowing effects are tried to be considered in the present study by simple assumptions depending on the sun incident angle on the individual satellite surfaces.…”

A shadow function model based on perspective projection and atmospheric effect for satellites in eclipse

“…In the orbit prediction tests, the force models used include SRP (Li et al, 2018), TRR (Thermal Re-radiation Pressure), ERP (Earth Radiation Pressure) (Li et al, 2017) and Antenna Thrust (the transmitted power is found in Steigenberger et al (2018)). The nominal attitude is applied during eclipses.…”