European Space Operations Centre

About: European Space Operations Centre is a government organization based out in Darmstadt, Germany. It is known for research contribution in the topics: Orbit determination & Satellite. The organization has 309 authors who have published 331 publications receiving 10399 citations. The organization is also known as: ESOC.

Long Solutions of Sequence A348480 of the On-Line Encyclopedia of Integer Sequences

Abstract: For numbers $x$ coprime to $10$ there exist infinitely many binary numbers $b$ such that the greatest common divisor of $b$ and rev($b$) = $x$ and the sum of digits of $b = x$ (rev($b$) is the digit reversal of $b$). In most cases, the smallest $b$ that fulfill these two constraints contain just a few zeros. But in some cases like for $x = 7, 11, 13$ and $37$, $b$ must contain more zeros than ones and these $b$ are called long solutions. For $11$ and $37$ it follows directly from the fact that these are porous numbers. For $7$ and $13$, the proofs that they have long solutions are presented in this paper.

In-flight measurement of Planck telescope emissivity

Abstract: The Planck satellite in orbit mission ended in October 2013. Between the end of Low Frequency Instrument (LFI) routine mission operations and the satellite decommissioning, a dedicated test was also performed to measure the Planck telescope emissivity. The scope of the test was twofold: i) to provide, for the first time in flight, a direct measure of the telescope emissivity; and ii) to evaluate the possible degradation of the emissivity by comparing data taken in flight at the end of mission with those taken during the ground telescope characterization. The emissivity was determined by heating the Planck telescope and disentangling the system temperature excess measured by the LFI radiometers. Results show End of Life (EOL) performance in good agreement with the results from the ground optical tests and from in-flight indirect estimations measured during the Commissioning and Performance Verification (CPV) phase. Methods and results are presented and discussed.

Slew Calibration for Spin-Stabilized Satellites

Abstract: The slewing of the rotation axis of a spin-stabilized satellite along a rhumb line by means of thrust pulses is addressed.Itisshown thatonecan calibratethemean thrustleveland themean pulsecentroiddelay independently from attitude knowledge before and beyond the slew. To achieve this one has to consider two successive slews or a slew broken down into two legs with different rhumb angles. The basic condition is that the thruster behavior is approximately equal in both legs. The required data are the solar aspect angles each time just before and just beyond the reorientation maneuvers. For the special case where the breakdown is made in two equal legs, called doglegs,ithasbeeninvestigatedwhichpathincreasehastobeexpectedandtowhichextenttheprobabilityincreases to end with a larger off-target error than with a single direct slew. Also the extrapolation of the initial attitude by using the planned maneuver data with corrrected calibration has been inspected by means of covariance analyses. In all of these aspects, the results of analyses are favorable. Finally, the calibration technique has been applied in three very large maneuvers on three similar spacecraft and the corresponding operational results are discussed. Nomenclature k = pulse strength calibration factor N = spin axis direction unit vector S = sun direction unit vector D att = angular difference between attitude estimates, deg d = declination in a sun coordinate system, rad ≤ = rhumb angle correction term, rad g = selected rhumb angle offset, rad h = sun angle, rad k = right ascension in a sun coordinate system, rad q = rhumb angle of a maneuver on the Mercator projection, rad r i = standard deviation of parameter i u = maneuver pathlength, rad {}0/e = parameter for initial/e nal attitude of a maneuver

Optimal manoeuvring between quasi-periodic orbits

Abstract: In the past halo orbits were used for most of the spacecraft missions going to the Lagrange point regions. However, other natural motions exist near these points presenting some advantages compared to halos. Quasi-periodic motions on invariant tori are associated with frequencies and amplitudes and surround the halo and vertical Lyapunov orbits. In this paper main characteristics of quasi-periodic orbits around the far-side Lagrange point in the Earth-Moon system are discussed. Optimal manoeuvres are identified to vary properties (phases, amplitudes) of an orbit. The proposed techniques utilise the stable manifold allowing for single manoeuvre transfers. The separation of spacecraft from a periodic orbit and a rendezvous scenario are discussed with respect to future missions, that have to cope with regular vehicle traffic, rendezvous and docking activities. Fuel-optimal transfers from a halo to a quasi-periodic orbit are identified in order to separate spacecraft. A second scenario assumes two spacecraft with a given phase separation on a quasi-periodic orbit. A target orbit is defined in which the spacecraft rendezvous. Parameter studies show that phase and amplitude changes strongly depend on the time when the manoeuvre is performed.