All Figures

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_01.eps} }\end{figure}$ Figure 1: Systematic disturbances in the two main components of the solar-radiation torques around the spin axis after removal of the modulation by the Earth-Sun distance variations. The disturbances around day 400 are also observed in other components of these torques around the spin axis, but not around the other two axes. The disturbances re-occurred after about 570 days, when the same alignment of the Sun, Earth and satellite orbit returned.
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In the text

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_02.eps} }\end{figure}$ Figure 2: The reconstructed magnetic moment for the y-axis. Significant variations took place on at least time scales of a few days. Determinations here cover periods of 40 orbits each (with a few individual determinations still left).
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In the text

$\begin{figure} {\includegraphics[width=7cm]{3193f_03.eps} }\end{figure}$ Figure 3: The power spectrum of the spin-synchronous harmonics in the torques acting on the spin axis. The three-fold symmetry of the satellite reflects in the relatively higher amplitudes for the 3rd, 6th, 9th and 12th harmonics. The line indicates values that would be equivalent to causing a 0.3 mas amplitude in the positional variations.
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In the text

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_04.eps} }\end{figure}$ Figure 4: The distribution of T2 statistics for the construction of the mean abscissa residuals per format of 10.7 s. The curves show the ideal Gaussian distribution for the same number of observations. The offsets towards lower T2 values are due to the weight limit applied to the brightest transits.
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In the text

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_05.eps} }\end{figure}$ Figure 5: An example of trend analysis, applied here to the calibration of the second-harmonic modulation parameters for the main detector, $\beta _4$ and $\beta _5$ (see also Sect. 4.3). Next to the discontinuities caused by re-focusing (vertical lines) disturbances can be seen on day 755 (orbit 1006, change of thermal-control electronics), days 779, 856 and 932 (orbits 1060, 1235 and 1407, re-starting the on-board computer), and day 818 (orbits 1150 and 1151, anomalous voltage). In each graph the upper set of data points refers to the following and the lower set to the preceding field of view.
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In the text

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_06.eps} }\end{figure}$ Figure 6: Abscissa residuals for one rotation of the satellite in orbit 401 (early May 1990). The top graph shows the residuals relative to the star mapper based attitude, and displays effectively the performance of that process. The bottom graph shows the same observations after the final iteration in the along-scan attitude fitting. The crosses and circles refer to observations from the preceding and following fields of view. The discontinuities in the upper graph reflect the effect of thruster firings.
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In the text

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_07.eps} }\end{figure}$ Figure 7: Residuals in rates ( top) and accelerations ( bottom) for the star mapper based attitude reconstruction. The data cover one rotation of the satellite. The large symbols refer to the along-scan direction, the small symbols to the spin-axis position. Data for orbit 52, 27 November 1989.
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In the text

$\begin{figure} {\includegraphics[width=8cm]{3193f_08.eps} }\end{figure}$ Figure 8: The distribution of formal errors on the modulation phase $\beta _3$ in arcsec, multiplied by the square root of the total photon count and the relative modulation amplitude M1 for the signal. Data for orbit 75.
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In the text

$\begin{figure} {\includegraphics[width=8.5truecm]{3193f_09.eps} }\end{figure}$ Figure 9: A log-log diagram of the mean formal errors on the predicted positions, as derived from the published catalogue, as a function of the total photon count for frame transits. The data for orbits 66 (open circles) and 1282 (dots) are shown. The formal errors for orbit 66, at the beginning of the mission, are clearly larger (as a result of uncertainties in the reconstructed proper motions) than for orbit 1282, half-way the beginning and end of the mission. The diagonal line shows the average photon-noise relation over the mission for a modulation parameter M1=0.72.
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In the text

$\begin{figure} {\includegraphics[width=8.5truecm]{3193f_10.eps} }\end{figure}$ Figure 10: A log-log diagram of the formal errors on the input data for the along-scan attitude reconstruction. Each data point represents 10.7 s of observations in one of the fields of view. The diagonal line is the photon noise relation, and the deviation towards the bright end reflects the formal accuracies of the predicted positions of the stars.
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In the text

$\begin{figure} {\includegraphics[width=8.5truecm]{3193f_11.eps} }\end{figure}$ Figure 11: Statistics on field transits. Left: histogram of the T2 statistics for the formation of field transits from frame transits. Right: normalised residuals between field transit abscissae and the predicted positions, for the third iteration. The curves show the equivalent Gaussian distribution for the same number of observations. The data are for orbit 409.
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In the text

$\begin{figure} {\includegraphics[width=11truecm]{3193f_12.eps} }\end{figure}$ Figure 12: The small-scale distortions as observed across the grid for field transits. Bottom: the actual distortions, showing as a regular pattern the 46 individual rows of scan fields. The large fluctuations represent the mean over the two fields of view, the much smaller fluctuations represent half the difference; middle: after correcting for a systematic non-linearity of the grid lines; top: After also correcting for mean scan-field tilt per row.
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In the text

$\begin{figure} {\includegraphics[width=8cm]{3193f_13.eps} }\end{figure}$ Figure 13: The final chromaticity corrections as derived from the accumulation of abscissa residuals in the astrometric parameters solutions. The full and dashed lines refer to data from the preceding and following fields of view respectively. A linear term (variable over the mission) has already been subtracted as part of the instrument-parameters solution.
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In the text

$\begin{figure} {\includegraphics[width=7cm]{3193f_14.eps} }\end{figure}$ Figure 14: The average distortion of the grid lines across a scan field as measured in frame transits. The seven curves show different intervals (covering each about 380 orbits) over the mission. The scan-field ordinate is normalised to the height of a scan field, 70.43 arcsec.
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In the text

$\begin{figure} {\includegraphics[width=7.5cm]{3193f_15.eps} }\end{figure}$ Figure 15: The dispersions in field-transit abscissae as a function of total transit photon count. The diagonal line is the Poisson-noise relation for average signal modulation amplitudes.
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In the text

$\begin{figure} {\includegraphics[width=7.5cm]{3193f_16.eps} }\end{figure}$ Figure 16: Dispersions in orbit-transit abscissa residuals as a function of magnitude. Squares: NDAC data; filled circles: FAST data; open circles: new reduction; crosses: new reduction normalised in observing time. The diagonal line represents the expected relation for photon-noise statistics.
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In the text

$\begin{figure} {\includegraphics[width=8.8cm]{3193f_17.eps} }\end{figure}$ Figure 17: Correlations in the abscissa errors at orbit level for the new reduction. The various measures taken in the new reduction have reduced the abscissa-error correlations by a factor 30 to 40, to a level where they no longer play a significant role. The second set of peaks is at the basic-angle interval of 58 $^\circ$ . The data are for stars brighter than 7th magnitude.
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In the text

$\begin{figure} {\includegraphics[width=8.8cm]{3193f_18.eps} }\end{figure}$ Figure 18: The precisions (formal errors) of parallaxes in the published data ( left) and the new solution ( right) as a function of magnitude. The bimodal structure in the plots reflects the scanning strategy: around the ecliptic poles the number of observations and their distribution is far more favourable for accurate parallax measurements than around the ecliptic plane.
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In the text

$\begin{figure} {\includegraphics[width=8.5cm]{3193f_02.eps} }\end{figure}$	Figure 2: The reconstructed magnetic moment for the y-axis. Significant variations took place on at least time scales of a few days. Determinations here cover periods of 40 orbits each (with a few individual determinations still left).
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$\begin{figure} {\includegraphics[width=7cm]{3193f_03.eps} }\end{figure}$	Figure 3: The power spectrum of the spin-synchronous harmonics in the torques acting on the spin axis. The three-fold symmetry of the satellite reflects in the relatively higher amplitudes for the 3rd, 6th, 9th and 12th harmonics. The line indicates values that would be equivalent to causing a 0.3 mas amplitude in the positional variations.
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$\begin{figure} {\includegraphics[width=8.5cm]{3193f_04.eps} }\end{figure}$	Figure 4: The distribution of T2 statistics for the construction of the mean abscissa residuals per format of 10.7 s. The curves show the ideal Gaussian distribution for the same number of observations. The offsets towards lower T2 values are due to the weight limit applied to the brightest transits.
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$\begin{figure} {\includegraphics[width=8.5cm]{3193f_07.eps} }\end{figure}$	Figure 7: Residuals in rates ( top) and accelerations ( bottom) for the star mapper based attitude reconstruction. The data cover one rotation of the satellite. The large symbols refer to the along-scan direction, the small symbols to the spin-axis position. Data for orbit 52, 27 November 1989.
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$\begin{figure} {\includegraphics[width=8cm]{3193f_08.eps} }\end{figure}$	Figure 8: The distribution of formal errors on the modulation phase $\beta _3$ in arcsec, multiplied by the square root of the total photon count and the relative modulation amplitude M1 for the signal. Data for orbit 75.
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$\begin{figure} {\includegraphics[width=8.5truecm]{3193f_10.eps} }\end{figure}$	Figure 10: A log-log diagram of the formal errors on the input data for the along-scan attitude reconstruction. Each data point represents 10.7 s of observations in one of the fields of view. The diagonal line is the photon noise relation, and the deviation towards the bright end reflects the formal accuracies of the predicted positions of the stars.
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$\begin{figure} {\includegraphics[width=8.5truecm]{3193f_11.eps} }\end{figure}$	Figure 11: Statistics on field transits. Left: histogram of the T2 statistics for the formation of field transits from frame transits. Right: normalised residuals between field transit abscissae and the predicted positions, for the third iteration. The curves show the equivalent Gaussian distribution for the same number of observations. The data are for orbit 409.
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$\begin{figure} {\includegraphics[width=8cm]{3193f_13.eps} }\end{figure}$	Figure 13: The final chromaticity corrections as derived from the accumulation of abscissa residuals in the astrometric parameters solutions. The full and dashed lines refer to data from the preceding and following fields of view respectively. A linear term (variable over the mission) has already been subtracted as part of the instrument-parameters solution.
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$\begin{figure} {\includegraphics[width=7cm]{3193f_14.eps} }\end{figure}$	Figure 14: The average distortion of the grid lines across a scan field as measured in frame transits. The seven curves show different intervals (covering each about 380 orbits) over the mission. The scan-field ordinate is normalised to the height of a scan field, 70.43 arcsec.
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$\begin{figure} {\includegraphics[width=7.5cm]{3193f_15.eps} }\end{figure}$	Figure 15: The dispersions in field-transit abscissae as a function of total transit photon count. The diagonal line is the Poisson-noise relation for average signal modulation amplitudes.
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$\begin{figure} {\includegraphics[width=7.5cm]{3193f_16.eps} }\end{figure}$	Figure 16: Dispersions in orbit-transit abscissa residuals as a function of magnitude. Squares: NDAC data; filled circles: FAST data; open circles: new reduction; crosses: new reduction normalised in observing time. The diagonal line represents the expected relation for photon-noise statistics.
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$\begin{figure} {\includegraphics[width=8.8cm]{3193f_17.eps} }\end{figure}$	Figure 17: Correlations in the abscissa errors at orbit level for the new reduction. The various measures taken in the new reduction have reduced the abscissa-error correlations by a factor 30 to 40, to a level where they no longer play a significant role. The second set of peaks is at the basic-angle interval of 58 $^\circ$ . The data are for stars brighter than 7th magnitude.
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$\begin{figure} {\includegraphics[width=8.8cm]{3193f_18.eps} }\end{figure}$	Figure 18: The precisions (formal errors) of parallaxes in the published data ( left) and the new solution ( right) as a function of magnitude. The bimodal structure in the plots reflects the scanning strategy: around the ecliptic poles the number of observations and their distribution is far more favourable for accurate parallax measurements than around the ecliptic plane.
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