Opening Sensors, Targets, Stars, and Planets

Many people like to use a new program right away without having to go through the time of reading a bulky manual.  This section will guide you through the basic operations of loading orbiting objects into Rendezvous and using the main window to propagate these objects to any desired time.

Opening New Sensor Constellations

In Rendezvous, a constellation is a related group of orbiting objects.  All the state vectors which describe the orbits of these objects is contained in one file.  To open up a constellation's state vector file, click the Constellation : Open Sensors... button in the main menu.  This will bring up a panel which looks like this:

Typically the state vector file will contain NORAD two-line elements for the sensor constellation, although other state-vector types are supported.  Two-line element files for currently orbiting objects can be found on the Web at many places such as

http://celestrak.com/NORAD/elements/

Now, navigate the OpenPanel path to the file Rendezvous.app/STATES/sat329.tle, and click the OK button at the bottom of the open panel.  After the file loads, the Sensors browser in the main window should show a selection labelled sat329.  Click on this entry and you will see entries for all the satellites in this constellation in the second browser column.

There are two pull-down menu buttons in the Open Panel.  The first button, labelled Sensor allows you to choose the specific kind of sensor you want to use.  For those who are not using Rendezvous-Pro, only the Generic Sensor is available.  The second button, labelled Platform, allows a user to select the type of orbit propagator which is used.  The AutoDetect selection will cause an appropriate propagator to be used based on the file extension (e.g. an SGP propagator is used for tle files).  If you would like to force a particular propagator to be used, select it before pressing the OK button.

Note: If you download other two-line element files, they must be named with a "tle" file extension.  Also, you must remove comments that may have been inserted into the file.  Many of these "tle" files have descriptive comments at the beginning and end of the files which can be removed with your favorite text editor.  The resulting file should contain only the names of the satellites and their corresponding orbital elements and be saved as an ascii file. Comments remaining in the files will confuse Rendezvous, and attempting to load such a file may cause the program to crash or produce incorrect results.

Displaying Ground Traces and Using the Calendar

Now suppose we would like to display the ground trace for MIR on Christmas Day 1998, at 9am GMT.

o Scroll the Sensors browser down to the MIR entry and double click on it.  When you do this, the MIR
entry will be labelled with a check mark to indicate it is being displayed, and a blue ground trace line
corresponding to the path MIR will take is shown on the Map in the main window.

o Set the year in the Calendar to 1998 using the appropriate arrow button
o Set the month in the Calendar to December using the appropriate arrow button
o Click on the 25 in the calendar,
o Set the hours in the clock to 9 by clicking directly in the hour field and using the up or down buttons next to the clock to advance to 9.

o Set the minutes in the clock to 00 by clicking directly in the minute field and using the up or down buttons next to the clock to advance to 00.
o Set the seconds in the clock to 00 by clicking directly in the seconds field and using the up or down buttons next to the clock to advance to 00.

Note: You may also set the clock by clicking the the field you wish to change and typing the value you desire.

After following this procedure, the main window should look like this:

The ground trace is plotted from the value in the Start field to the value in the End field of the Ground Trace Control section.  In this case, the MIR ground trace is plotted from 0 seconds to 1500 seconds, measured from the time and date set in the Calendar.  The ground trace is plotted in increments of 100 seconds, which is the value in the Delta T field.  Notice the little icon of MIR is located at the beginning of the ground trace.  If you would like the icon to be located at the end of the ground trace, enter the value 1500 in the MET (Mission Elapsed Time) field of the Ground Trace Control section.  If you would like to display the ground trace of a complete orbit, enter the value 5600 in the End text field of the Ground Trace Control box of the main window (MIR has an orbital period of 5600 seconds).

Opening New Target Constellations

Opening targets files is nearly the same as opening sensor files.  State vector files can be used with either Sensors or Targets.

o Click on the Constellation : Open Targets... button in the main menu.
o Navigate to the Rendezvous.app/STATES/sat329.tle file again and click the OK button.  At this point, the entry sat329 should appear in the Targets browser.
o Click on this entry to display the list of all the targets available.
o Scroll down the target list to the entry labelled IRAS and double-click on it

The ground trace of IRAS depicting its path will now appear as a red line on the map.  A great deal of information can be displayed on the map.  Go here for more information on the capability and use of the Ground Trace maps.



Opening Star Databases

Rendezvous ships with a small version of the SAO stellar database which includes stars down to magnitude 5.5. These stars can provide a background reference in the Telescope Inspector's boresight view, and they can be included as radiometric point sources in the focal plane simulations.  Several other databases are available on request (full SAO, FK5, and MSX databases).  Since Rendezvous implements these as loadable bundles, custom databases can be included quite readily.

Opening the star files is very similar to opening sensors or targets.  In this section, we'll open the SAO55 database and have a look using the Telescope Inspector.

Load the SAO star database

o Click the Constellation : Open Stars... button in the main menu
o Click the Platform pull-down menu at the bottom of the Open panel and select the SAOStar entry
o Navigate to the Rendezvous.app/STATES/SAO55 file, and click the OK button
o Double-click the SAO55 entry in the Stars browser of the main window

Load a sensor at Albuquerque

o Click the Constellation : Open Sensors... button in the main menu
o Navigate to the Rendezvous.app/STATES/USCities.gnd file, and click the OK button
o Click on the USCities entry in the first column of the Sensors browser in the main window
o Double-click on the Abq,NM entry in the second column of the Sensors browser in the main window

Set the Epoch Date and the Time

o Set the Date to January 22, 1999 in the Calendar of the main window
o Set the Time to 0 : 00 : 00 in the Clock in the main window

Bring up a Telescope Inspector and set its field of view

o Click on the Inspectors : Sensor... button in the main menu
o Select the Telescope button in the Detail area of the Sensor Inspector panel
o Enter the value -30 (that's a negative 30) in the Az Min: text field in the Field of View Extent area of the Telescope Inspector panel, then press the TAB key on the keyboard to advance to the next field
o Enter the value 30 in the Az Max: text field, and press the TAB key
o Enter the value -30 (again, this is a negative 30) in the El Min: text field, press the TAB key
o Enter the value 30 in the El Max: text field, press the Carriage Return key

Set the boresight direction for the sensor

o Select the J2000 button in the Scan Boresight area of the Telescope Inspector panel
o Enter the value 12 in the RA text field of the Scan Boresight area of the Telescope Inspector, and press the TAB key to advance to the next text field
o Enter the value 55 in the Dec text field of the Scan Boresight area and press the TAB key
o Enter the value 0 in the Roll text field area, and press the Carriage Return key

You should see the Big Dipper approximately in the center of the field of view like this:


Opening Planets

Rendezvous can also display the nine major planets and any other body that can be expressed with a helio- centric orbital element set.  These bodies are loaded into Rendezvous as Targets.  We'll load the planets in first.

If you haven't already done so, Set the Epoch Date and Time:

o Set the Date to January 22, 1999 in the Calendar of the main window
o Set the Time to 0 : 00 : 00 in the Clock of them main window

Now, open the Planets:

o Click the Constellation : Open Targets... button in the main menu
o Click the Platform pull-down menu near the bottom of the Open panel, and select either the AutoDetect entry or the PolynomialPlanet entry
o Navigate to the Rendezvous.app/STATES/PolynomialPlanet.list file, and click the OK button
o Double-click on the PolynomialPlanet entry in the first column of the Targets browser of the main window
o Double click on the Earth entry in the second column of the Targets browser of the main window.  This is intended to de-select the Earth for this exercise

Just for the fun of it, let's make the Telescope track the moon, and see if there's anything interesting there

o Press the Attitude Processor pull-down menu in the Sensor Inspector panel, and select the TrackingAttitude entry
o Double-click on the Moon entry in the Target browser of the Telescope Inspector panel.  Notice we're doing this action in the Telescope Inspector panel, NOT the main window.

Zoom the field of view:

o Enter the values -5 and 5 in the Az Min and Az Max text fields of the Telescope Inspector
o Enter the values -5 and 5 in the El Min and El Max text fields of the Telescope Inspector, and press the Carriage Return button.

You should see the the crescent moon in the center of the display, with a purple dot to the "north-east".  This purple dot is Jupiter.  The view is shown here:

We can view the Planets in another way, using the SolarSystem Inspector.  Let's take a look at the Solar System:

o Double-click the Earth entry in the Targets browser of the main window to re-enable the earth for display
o Click the Inspectors : Solar System button in the main menu

A panel appears which looks like this:

This view depicts the solar system out to a radius of about 2 astronomical units (the value in the Field of View text field in the upper-right side of the panel).  The sun is the yellow ball in the center, and the orbits of the first four planets (Mercury, Venus, Earth, and Mars) are plotted as blue ellipses.  The positions of the planets at the Epoch Date and Time set in the main window are shown as the light-blue balls.   Changing the value in the calendar will update this panel with the new positions.  Click-dragging the mouse will change the viewpoint of the panel.  Dragging the mouse in a vertical direction will change the viewpoint latitude while dragging the mouse horizontally will change the viewpoint longitude.  The orbits are displayed as a blue color when looking at them from above.  However, the color changes to purple when the viewpoint has been click-dragged to view them from below.

The two red lines indicate the axes in the ecliptic plane.  The bright red axis pointing to the right is the X axis and lies along the vernal equinox.  The darker red line pointing toward the top is the Y axis.



Opening Comets

Finally, let's demonstrate how to open a comet file, or any other type of body which is described by a heliocentric orbital element set.

o Click the Constellation : Open Targets... button in the main menu
o Click the Platform pull-down menu near the bottom of the panel and select either the AutoDetect entry or the FGComet entry
o Navigate to the Rendezvous.app/STATES/Comets.hce file and click the OK button
o Click the Comets entry in the first column of the Targets browser in the main window
o Double-click the Hale-Bopp entry in the second column of the Targets browser in the main window

The Solar System Inspector now looks like this when click-dragged to a view orienation which has a latitude of 30 degrees and a longitude of 270 degrees: