TVNSP nearcraft carry a Central Computer/Programmable Sequencer (CC/PS) to operate each mission. The heart of the CC/PS is the Basic Stamp 2-IC, which is programmed prior to each mission. Portions of the flight code remain constant, from flight to flight. Other portions of the flight code, those dealing with specific experiments for instance, are changed for each mission. The portions that remain constant are referred to as the Command Telemetry, since this telemetry focuses on the status of the nearcraft's command module. Command Telemetry from each TVNSP nearcraft launched consists of an endless repetition of data (that is, endless until the nearcraft is powered down). The format for the Command Telemetry changes during the different facets and phases of a mission.
Each mission consists of two facets, the Preflight Facet (PreF) and the Flight Facet. The Flight Facet consists of two phases, Ascent Phase (AscPh) and Descent Phase (DscPh). Preflight begins at nearcraft power up and continues for approximately five minutes. A simple software timer determines the end of Preflight Facet. At the end of the Preflight Facet, TVNSP nearcraft automatically enter the Flight Facet. As long as the onboard GPS provides valid data, the change in nearcraft altitude determines when the phase of the Flight Facet changes. In future flights, an onboard barometric altimeter will be used should the GPS receiver fail. The initial phase of the Flight Facet is Ascent Phase. When a greater than 100 meter drop in altitude is detected, the nearcraft enters Descent Phase. The CC/PS can force a change in Flight phase should the GPS receiver lose satellite lock, but later recover.
The data format of PreF is organized into the following fields.
 |
PreF T-5
| R-5 GPS
| NMEA GPGGA sentence
| NMEA GPRMC sentence
| 1000 ft
| R-5,B-CH1,2015,B-CH2,1045,B-CH3,960,B-CH4,4000,B-CH5,1006,B-CH6, 1467,B-CH7,2148,B-CH8,3904, |
The above data repeat four times every minute. At each minute the T-5 and R-5 decrements until it reach zero. At T-0, the nearcraft enters the Flight Facet of its mission. The five minutes required to enter the Flight Facet should be sufficient to launch a near space stack.
When the countdown has reached zero, the nearcraft transmits the following text:
|
Lift Off |
Now the nearcraft enters the Flight Facet, beginning with the Ascent Phase.
The data format of Flight Facet is organized into the following fields.
|
TV NSP Flight (mission number)
| (this flight's message)
| R-1Stat (either AscPh or DscPh)
| R-1 GPS
| NMEA GPGGA sentence
| NMEA GPRMC sentence
| 1000 ft
| R-1,B-CH1,2015,B-CH2,1045,B-CH3,960,B-CH4,4000,B-CH5,1006,B-CH6, 1467,B-CH7,2148,B-CH8,3904,
| R-1Exp
| NMEA GPGGA sentence
| NMEA GPRMC sentence
| (data from experiments) |
The above data repeats until the nearcraft is powered down. When the balloon burst is detected, the Phase field changes from AscPh to DscPh.
Data from experiments will be proceeded with a field identifier followed with a value. Before each flight, the format for experimental data should be published. In any case, after each flight, experiment data will be made available to the public after the principal investigator (PI) has had time to analyze the results.
The CC/PS is capable of detecting many conditions. These conditions are divided into two categories, Critical Errors and Status Messages. Critical Error messages appear in capital letters, while the Status Messages appear in a mix of capital and lower case letters. In the future the number of detectable conditions will increase and the CC/PS will be programmed to respond appropriately to them.
NOGPS
When the GPS has failed to respond within 30 seconds of being given a command
GPS SPOOF
When the CC/PS determines the detected drop in altitude was caused by a bad NMEA
field
BAD GPS DATA
When the increase in altitude is greater than 500 meters or the decrease in
altitude is greater than 1000 meters (both are greater than what is normally
expected)
NO DELTA ALT
When the change in altitude is less than 100 meters (within SA error limits)
Baro#Phase
The change in barometric pressure doesn't match the current flight phase
GPS Burst
The CC/PS has detected a 100 meter or greater drop in altitude based on GPS data
Baro Burst
The CC/PS has detected a drop in altitude based on barometric altimeter data