Untersuchung zur Genauigkeit der ROSAT-Magnetfeldmessungen

Die Genauigkeit der Messungen des ROSAT Magnetometers wird durch Vergleich mit Modellen bestimmt. Der Einfluss von Spulenstroemen an Bord des Satelliten auf die Messungen wird diskutiert

Analyse des ROSAT Scan Modes im Aug. 91

Der waehrend des Monats August 1991 durchgefuehrte ROSAT Skysurvey wird untersucht. die Problemedie sich aus der schlechten Genauigkeit der Kreisel ergeben, werden beschrieben

Investigation of the contribution from peripheral GnRH-like immunoreactive 'neuroblasts' to the regenerating central nervous system in the protochordate Ciona intestinalis

The neural ganglion of the ascidian Ciona intestinalis regenerates in its entirety within a few weeks of ablation. Here we investigate the role of gonadotropin-releasing hormone-like immunoreactive (GnRH-li) cells in regeneration. Immunocytochemical studies show that in addition to a previously described plexus of GnRH-like neurones located in association with the dorsal strand, the normal adult brain contains GnRH-li neurones. These are predominantly localized to the ventral cortical rind at the posterior of the ganglion. Following ablation, non-process bearing GnRH-li cells appear in the regenerating area within two days. By day 8 post-ablation, process bearing GnRH-li cells are detected close to the regenerating brain. The number of these cells increases at later stages. GnRH-li cells are first detected within the regenerating brain at 14 days post-ablation and their number subsequently increases. These cells are initially concentrated along the ventral surface of the regenerating brain near to the dorsal strand. Double labelling studies with bromodeoxyuridine show that none of the GnRH-li cells are labelled at any stage of regeneration. The data are consistent with a sub-population of the new neurones being derived from GnRH-li neuroblasts born prior to ablation, which migrate from the dorsal strand complex into the regenerating ganglion

On-orbit control system performance of the ROSAT spacecraft

The on-orbit performance of the attitude control system of the ROSAT spacecraft is described. It is performing both precise pointing observations and scanning over the sky. The control system consists of high precision star trackers and gyros for attitude reference and reaction wheels for maneuvers. Since launch on 1 June 1990 first the checkout and calibration phase was performed, indicating that pointing accuracies <1 arc min, slew maneuver accuracies <4 arc min, and scan accuracies <13 arc min are achieved. These are, like all other performance values, well inside the specifications. Since 30 July, the sky survey is in progress without problems. The magnitude calibration of the star trackers and one type of anomaly detected during the survey are discussed additionally

Untersuchungen zur STC-Genauigkeit.

Die Positionsgenauigkeit von Sternsensormessungen wird untersucht. Die Relativabstaende veraendern sich um mehr als 5 Bogensekunden. Dies ist um einen Faktor 3 groesser als Labormessungen ergeben haben

IN-FLIGHT SENSOR PERFORMANCE OF THE ROSAT SPACECRAFT AND CONSEQUENCES FOR THE ATTITUDE RECONSTRUCTION ON GROUND

The scientific payload of the ROSAT-Spacecraft consists of a large X-ray telescope carrying two Proportional Counters together with a High Resolution Imager and smaller XUV-telescope called Wide Field Camera. The success of the ROSAT-mission depends significantly on the accuracy of the final attitude solution on ground based on rate integration gyro and star tracker camera measurements. So the performance of these attitude measurement devices influences directly the quality of the attitude solution

Untersuchung zum Verhalten der ROSAT-Kreisel

Die ROSAT Kreiselprobleme werden beschrieben. Sie aeussern sich in drehrichtingsabhaengigen Driftwerten und zu grossen Abweichungen des Skalenfaktors vom Nominalwert. In beiden Faellen werden die Spezifikationen verletzt

The ROSAT star tracker-flight experience

A high precision star tracker was developed for the attitude measurement and control system of the German X-ray astronomy satellite ROSAT, which was launched on 1 June 1990. This star tracker has a basic pointing angle of around 0.5 arc second per axis in a 5.9 deg x 4.4 deg field of view, whilst tracking stars down to 7th magnitude. It also has to operate with reduced accuracy in the sky survey phase of the mission, when stars scan across the field of viewin a given direction with a rate of up to 5 /minute. The performance exceeds specification as demonstrated by ground test and flight data reported in this paper. The star tracker is a solid-state instrument based on a CCD image sensor. It has been qualified since 1985, and is the highest accuracy solid-state tracker flown by western European industrie to date