is the work-script for chapter 3
11 October 2017
3.1 Power systems
about solar cells, the solar constant, the variation in
illumination and batteries.
Click here for animation how solar panels are deployed.
a link to a description of a new type of battery.
We looked at the variation of illumination and made sure
that we understood every variable in the equation.
3.2 Attitude and orbit control
We then focussed on the control system for keeping the
satellite in a particular orientation (attitude).
We talked about the sources of
rotational torque. We leaned about earth, sun and star sensors
and how an
erroneous attitude is corrected. We then focused on the three-axis stabilization.
We looked at nutation
dampers. We looked at the engineering model of the RadioAstron
spacecraft. We also saw the focus
tanks and the gas
18 October 2017
We covered issues related to the
orbit control and compared the fuel allocations for various
3.3 Telemetry, tracking and command (TT&C)
We talked about the measurement of the orientation, the
environment and the health of a satellite
and how these measurements are transmitted. Then we
covered issues related to the tracking
of a satellite. We talked about how commands are executed.
We learned about allocated
UHF 0.8 -
1.2 - 1.7 GPS
We learned about uplink and downlink.
20 October 2017
We interpreted the block diagram
of a transponder.
23 October 2017
We discussed the TWTA and
compared it to the amplification in the magnetic field
of a pulsar. We learned about solid-state power
amplifiers, FETs and HEMTs. We discussed intermodulation noise,
how it is generated and how it affects the spectrum.
We covered three types of antennae, the wire
antenna or Hertz dipole, the horn antenna and the
reflector antenna. The Hertz dipole was the antenna
Heinrich Hertz used to discover radio waves. Click here
for a description of the dipole and how an EM wave
in space pushes electrons in a dipole back and forth and
generates a voltage between the two elements of a dipole
and a current through them. The most famous horn
antenna is the one Penzias and Wilson used to
improve satellite communications and found by chance the
microwave background radiation which is the
strongest evidence we have for the Big Bang theory.
Small versions of the horn antenna are similar to feeds,
or feed horns, which are used on satellites for a
broad coverage and also in the focal area of reflector
antennas are used on satellites to direct
information to small areas of the Earth. Large
reflector antennas are shown here
about spot beam technology and the radiation pattern or beam
pattern or the beam of a telescope. We also learned
about the gain of a telescope and the degradation of the gain
as a function of the rms surface variations with respect to a
for a 3-dim beam pattern of a paraboloidal antenna. Click
for figures of beam patterns as a function of gain and