Safe Picosatellite Release from a Small Satellite Carrier

Abstract

The Berlin Infrared Optical System satellite, which is scheduled for launch in 2016, will carry onboard a picosatellite and release it through a spring mechanism. After separation, it will perform proximity maneuvers in formation with the picosatellite solely based on optical navigation. Therefore, it is necessary to keep the distance of the two spacecraft within certain boundaries. This is especially challenging because the employed standard spring mechanism is designed to impart a separation velocity to the picosatellite. A maneuver strategy is developed in the framework of relative orbital elements. The goal is to prevent loss of formation while mitigating collision risk. The main design driver is the performance uncertainty of the release mechanism. The analyzed strategy consists of two maneuvers: the separation itself, and a drift-reduction maneuver of the Berlin Infrared Optical System satellite after 1.5 revolutions. The selected maneuver parameters are validated in a Monte Carlo simulation. It is demonstrated that both the risk of formation evaporation (separation of more than 50 km) as well as the eventuality of a residual drift toward the carrier are below 0.1%. In the latter case, formation safety is guaranteed by a passive safety achieved through a proper relative eccentricity/inclination vector separation. Notation a = semimajor axis of the carrier satellite, m e = eccentricity of the carrier satellite e i = delta-v error on the ith tangential component, m∕s f i = simulated performance factor of maneuver i i = inclination of the carrier satellite, deg k = odd natural number n = mean angular motion of the carrier satellite, rad∕s p = real number u = mean argument of latitude of the carrier satellite,°v = absolute value of velocity vector, m∕s ΔB = differential ballistic coefficient, m 2 ∕kg Δ• = finite variation of a quantity δα = nondimensional relative orbital elements set δe = nondimensional relative eccentricity vector δi = nondimensional relative inclination vector δλ = nondimensional relative longitude δv R , δv T , δv N = instantaneous velocity changes in local radial-tangential-normal frame, m∕s δ• = relative quantity ϵ xi , ϵ yi , ϵ zi = simulated errors of the carrier attitude control during maneuver i, rad θ = argument of latitude of the relative ascending node,°ξ = phase change of the relative eccentricity vector, rad ρ = atmospheric density, g∕km 3 φ = argument of latitude of the relative perigee,°χ = function of the difference between the arguments of latitude of the two maneuvers Ω = right ascension of ascending node of the carrier satellite, deg ω = argument of perigee of the carrier satellite, deg

Flight Demonstration of Autonomous Noncooperative Rendezvous in Low Earth Orbit

“…This third-party, independent, experimental activity, in fact, has been used as noncooperative target for the sake of the AVANTI demonstration. BEESAT-4 has been released in-orbit on the 9 th of September 2016 by means of a single picosatellite launcher device which provided an equivalent separation delta-v of circa 1.5 m/s (see details on the separation strategy design [26,27] and in-flight events [1]).…”

In-orbit experience and lessons learned from the AVANTI experiment

“…Afterwards, on the 9 th of September 2016, BIROS released BEESAT-4 in-orbit by means of a single picosatellite launcher device which provided an equivalent separation delta-v of circa 1.5 m/s. 6,7,2 While carrying out its independent experimental activities, BEESAT-4 has been used as noncooperative target for the sake of the AVANTI demonstration.…”

“…Within AVANTI, for example, for safety reason the element with larger ballistic coefficient (i.e., the target) lead the formation in flight direction, so that the natural effect of the differential aerodynamic drag made the satellite to drift apart form each other. 6 Regarding the relative motion, the exploitation of passively safe relative orbits translate in the constraint of setting a specific phasing of the relative eccentricity and inclination vectors (i.e., 0 or 180 degrees). By combining this requirement with the delta-v consumption aspect, the most appealing option is to target δe x = δi x = 0 (as performed in AVANTI).…”

Design challenges and safety concept for the AVANTI experiment

“…Together, the picosatellite ejection strategy and the orbit correction maneuvers performed after the first on-ground picosatellite orbit determination ensure that the relative orbit, at the start of the experiment, is passively safe. 19 After the activation of AVANTI, the guidance module ensures that the safe phasing of the relative eccentricity and inclination vectors is kept throughout all the maneuvers required for the rendezvous. 11 Therefore, it becomes possible to always maintain a desired minimum distance in the radial-normal plane by simply avoiding too small relative orbits or rapid changes of relative mean longitude (since a large relative semi-major axis induces a large shift in the radial direction).…”