1. AGBell -1- Build the A Train Constellation using STK To build the “ideal” A Train constellation we will use STK - Satellite Tool Kit by AGI We would like to add the 8 AFSCN Ground Stations that support CloudSat.

2. AGBell -2- Build the A Train Constellation using STK This diagram shows how ground command and telemetry are handled for CloudSat As can be seen the AFSCN – Air Force Space Control Network is used. We want to add Ground Stations for command and control of CloudSat

3. AGBell -3- Build the A Train Constellation using STK http://www.responsivespace.com/Papers/RS6/SESSIONS/SESSION%20I/1006_HODGES/1006P.pdf CloudSat uses eight ground stations located around the world to collect telemetry and upload commands to the satellite. The 8 Ground Stations are: CTS DGS GTS HTS NHS TCS TTS VTS

4. AGBell -4- Build the A Train Constellation using STK Select Insert>Facility From Facility Database Then select Advanced>Network> USAF AFSCN

5. AGBell -5- Build the A Train Constellation using STK The 24 USAF AFSCN Ground Stations are shown below and then select the “Insert” button Select the 8 Ground Stations that CloudSat uses: CTSA DGSA GTSA HTSA NHSA TCSA TTSA VTSA

6. AGBell -6- Build the A Train Constellation using STK The 8 Ground Stations are then displayed in yellow on the globe. These Ground Stations are distributed around the world to minimize the amount of information that must be stored by the satellites.

7. AGBell -7- Build the A Train Constellation using STK We want the Access for CloudSat to the 8 ground stations.

8. AGBell -8- Build the A Train Constellation using STK Select all the Ground Stations and Select Compute Then select the 8 Ground Stations Next, lets “compute” the Access time from CloudSat to the eight Ground Stations

9. AGBell -9- Build the A Train Constellation using STK In the 3D view a link between GTSA and CloudSat is shown. As the satellites orbit the Earth other Ground Station will be linked as CloudSat moves through its orbit. Click on the picture to see the scenario.

10. AGBell -10- Build the A Train Constellation using STK We can also generate a report to show when and how long each Ground Station has access to CloudSat.

11. AGBell -11- Build the A Train Constellation using STK We can also view the Access time in a graphical view. CloudSat orbits the Earth about 14 times per day.

12. AGBell -12- Build the A Train Constellation using STK The combined access time for a 1 day scenario can be created using the access data which can be captured as a CSV file. Max Access Time = 75 min Min Access Time = 5 min Ave Access Time = 34 min StDev Access Time = 25 min Minutes starting from 18 March 2010 12:00 AM No Access Access This type of information can be used to determine the amount of on-orbit storage needed and download data rates required.