This exercise simulates the operation of a large radio telescope used to
determine the rate of rotation of a planet by Doppler radar.  Begin by
selecting "Log In" on the main menu, and fill in the requested
information.  After completing the log-in, select "Start" on the main
menu.

The control panel that appears has only three pushbutton controls.
Begin by pressing the "Tracking" button to turn on the sidereal drive
and activate the other controls.

If you have a set of coordinates and the distance from the Earth to the
target planet, press "Set Coordinates", respond "OK" to the message that
appears, and enter the coordinates and distance on the dialog that
appears.  When you have finished press "OK" and the telescope will begin
slewing.

In most instances you will not have a set of planetary coordinates.  If
this is the case, do not press "Set Coordinates" yet (or if you have
already done so, press "Cancel" on either the message or dialog that
follow).  Select "Ephemeris" from the main menu.  If your instructor
has given you a specific date and time, enter them on the dialog that
appears, otherwise use the default (current date and local time) values.
Press "OK" to compute the ephemeris.  Leave the results window on the
screen or minimize it (do not close it), and press "Set Coordinates".
Respond "Yes" to "Use Computed Values?" and the telescope will begin
slewing.  (If you left the Ephemeris Computation window on the screen it
will minimize when the slew starts.  If you minimized it, it remains
minimized and you can reopen it for reference.)

When the slew is complete, the red "Slewing" light will go out, and a
"Slewing Completed" message will appear, along with a display showing
the relative positions of the Sun, the Earth, Mercury and Venus on the
date and time of the Mercury coordinates you have used.  The telescope's
pointing coordinates will appear on the control panel.  (If you now turn
off the drive by pressing the "Tracking" button you will notice that the
right ascension increses as the Earth turns.)  When you are satisfied
that the telescope is aimed correctly, press the "Send Pulse" button to
transmit a radar pulse towards the planet.  A "Pulse Sent" message will
appear on the screen, along with the estimated time until reception of
the return pulse.  The message appears in yellow when the reflected
pulse is returning, and the time appears in red during the last 30
seconds until anticipated reception.

A window showing the initial shape of the pulse also appears on the
screen when the pulse is transmitted.  This window will minimize itself
after 10 seconds.  When that occurs you will see an animated display on
the telescope screen.  The bright radar pulse moves toward Mercury and
then the fainter echo returns.  (The pulses move at the speed of light
relative to the scale of the display.  The distances on the display are
correctly scaled, the images of the Sun, Earth, and Mercury are much too
large.)

If for any reason you wish to stop waiting for a return pulse, press
"Send Pulse" again, and respond "No" to the message that appears.

