In this paper I will describe a new software package developed using the Javaprogramming language, aimed to compute the positions of any Solar System body(among asteroids, comets, planets, and satellites) to help to performcross-matches of them in observations taken from earth- and space-basedobservatories. The space telescopes supported are Hubble, James Webb, Euclid,XMM-Newton, Spitzer, Herschel, Gaia, Kepler, Chandra, and TESS, although theflexibility of the software allows to support any other mission without theneed to change a single line of code. The orbital elements can be selectedamong the asteroid database from the Lowell observatory (completed with thecometpro database of comets maintained by the LTE), and the JPL database ofminor bodies. The software does not depend on external tools, and performs its ownnumerical integration of minor bodies. The dynamical model implemented for theSolar System includes the gravity effects of all major bodies, including theEarth, Moon, and Pluto as individual bodies, 16 perturbing asteroids as inother tools, the General Relativity effects, the oblateness of the Sun, Earth,and Moon, and the non-gravitational forces for both comets and asteroids. Acomplete set of web services allow to compute the cross-matches (that are laterto be confirmed, for instance by visual inspection of the images) and alsoephemerides of specific bodies. The code is highly optimized and follows thehighest standards in terms of software quality and documentation.
In any spacecraft landing mission, fuel-efficient precision soft landingwhile avoiding nearby hazardous terrain is of utmost importance. Very fewexisting literature have attempted addressing both the problems of precisionsoft landing and terrain avoidance simultaneously. To this end, an optimalterrain avoidance landing guidance (OTALG) was recently developed, which showedpromising performance in avoiding the terrain while consuming near-minimumfuel. However, its performance significantly degrades in the face of externaldisturbances, indicating lack of robustness. To mitigate this problem, in thispaper, a near fuel-optimal guidance law is developed to avoid terrain andachieve precision soft landing at the desired landing site. Expanding the OTALGformulation using sliding mode control with multiple sliding surfaces (MSS),the presented guidance law, named `MSS-OTALG', improves precision soft landingaccuracy. Further, the sliding parameter is designed to allow the lander toavoid terrain by leaving the trajectory enforced by the sliding mode andeventually returning to it when the terrain avoidance phase is completed. Andfinally, the robustness of the MSS-OTALG is established by proving practicalfixed-time stability. Extensive numerical simulations are also presented toshowcase its performance in terms of terrain avoidance, low fuel consumption,and accuracy of precision soft landing under bounded atmospheric perturbations,thrust deviations, and constraints. Comparative studies against existingrelevant literature validate a balanced trade-off of all these performancemeasures achieved by the developed MSS-OTALG.