Horizon Crossing Indicator versus Time

This plot of the time difference between Horizon Crossing Indicator limb crossings shows spin-axis nutation being damped out during the first few orbits. The broad envelope of the line at left is due to nutation; as time passes it reduces in amplitude and finally becomes a narrow trace, showing that the passive alcohol-filled ring nutation damper is doing its job.

Spin Period

Spin period of the satellite during the second day of operation. The trend is due to the gradual slowing of the spin while the once-per-orbit fluctuations are due to expansion and contraction of the spacecraft in response to heating and cooling during the day/night cycle.

Right Ascension and Declination

Right ascension and declination of the spacecraft spin axis over the course of four orbits. The spin axis is making a twice-per-orbit cycle about a point near orbit normal, with an amplitude of about one degree. This may be due to the residual magnetism of the spacecraft and its torque rods. With the axial torque rod last activated in the negative state, the spin axis epicenter is precessing at almost the same rate as orbit normal, the motion of which is shown on the plot as a heavy, straight line.

Plots of Spacecraft Temperatures

Plots of Spacecraft temperatures for three locations on the 4th day of operation. The top plot is the central baseplate temperature (on the launch adapter side). It shows about a 4 degree C day/night amplitude. It is cooling slightly over time because just before this interval all 4 solar array string circuits were on, which dumps more heat through the batteries. With 3 circuits on the central plate is equilibrating to a 16-20 C range. The batteries, subsytem electronics boxes, and instruments are closely following the central plate temperatures. The second plot shows the launch adapter ring temperature. The launch adapter is on the sun side of the spacecraft, and the marmon clamp is fairly absorptive, so 20 degree swings are seen. These fluctuations are not conducted significantly to the central plate, however. The third plot shows a solar panel temperature changing by about 40 degrees. This is as designed - the solar panels are insulated from the rest of the spacecraft, so the components do not see these temperature swings.

Plot of Solar Array Current and Shunt Current

Solar array current and shunt current during the solar eclipse of 26 February, 1998. The spacecraft passed through a region of partial eclipse six orbits after launch. A slight dip can be discerned in the total array current generated, while the shunting of excess current went almost to zero.

Plot of Solar Sensor Data

Solar sensor data from 28 February 1998 (the third day of operation), with 200 spins overplotted. The solar beta angle is 28.5 degrees, the SXP offset angle is 22.5 degrees, and the spacecraft is 1 degree off orbit normal, resulting in a maximum Y-axis measurement of 5 degrees.

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Plot of Raw Data from UV Spectrometer

Raw data from the Ultraviolet Spectrometer shortly after turn-on on 3/3/98. 50 spins during a sunrise sequence showing Rayleigh scattering from the forward limb are plotted. The integration intervals are "spread out" over a quarter-spin instead of concentrated on the limb, to obtain a low-resolution check on the data.

Plot of Raw Limb Scans

Raw limb scans from UVS channel 1 on 3/10/98 at 20:32 UT near the northern hemisphere auroral zone. 15 scans (represented by red dots) are averaged to obtain the heavy black line. The fluorescent (1,0) gamma band emission at 215 nm is seen above 100 km tangent altitude. The bright Rayleigh scattering layer in the middle atmosphere is also identified.

Plot of Solar X-ray Photometer Data

Raw Solar X-ray Photometer data from channel 2 (the titanium-coated diode) with the door open and closed. 50 scans from 3/2/98 (the fifth day of operation) are overplotted. By subtracting the door-closed signal from the door-open signal, the solar X-ray flux in the 2-16 nm range is obtained.

Plot of Auroral Photometers First Orbit

The first orbit of Auroral Photometer data on 3/5/98 with the integration time at 65 ms. Nadir data from channel 1 is plotted, one point per satellite spin, and the major geophysical features identified.

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