1. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 1 ANITA Command, Control and Monitoring Jim Beatty Penn State

2. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 2 Some background… LDB system documentation is now under revision. Most of my experience is in the conventional balloon program.

3. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 3 How do we turn it on? Discrete commands activate open-collector control pulses (~100 ms) which can be used to trigger aerospace-grade mechanical latching relays. –Two commands are needed per relay (on-off) –Relays can be obtained through NSBF These relays can be used to activate the actual power-handling relays or to enable power supply outputs. –Main relays most likely solid-state devices. This type of command can also be used to enable heaters.

4. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 4 When it is off… We should be able to arrange to monitor some key temperatures and voltages (e.g. flight computer area, power system temperatures and voltages) to ensure they are within the operating range before applying power to the instrument.

5. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 5 Control of the Instrument State When the instrument is operating, commanding should consist of simple state changes, encoded as 16-bit data words. –Avoid complicated sequences Some people try using this facility to download tables or code; this rarely works due to lost commands. We need to design the observing strategy with simplicity of control in mind. –A command should never be used to toggle a variable or step through a sequence. Commands frequently fail to go through (e.g. due to CRC errors) –Dangerous actions should require an ‘arm-fire-disarm’ sequence. A structured division of the data word has been useful in the past (e.g. (type:address:parameter)). The data word received should be echoed in the telemetry stream. –Include ‘last command’ as a housekeeping variable (echo until new command received in case the first echo frame is dropped) The complete instrument state should be available in the housekeeping data (perhaps subcommutated) so that command effect can be verified.

6. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 6 Some useful commands to include… Several levels of reset commands should be implemented which can set the flight software or individual subsystems to a reference state or restart if necessary. A discrete command should be wired to the computer hard reset switch to allow a hard reset without cycling power.

7. = Particle Astrophysics ANITA Collaboration Meeting UC-Irvine November 24-25, 2002 7 Commanding software and protocol A simple program should be used to issue the command words to the NSBF computer, providing a ‘tired scientist friendly’ interface with error checking and an opportunity to verify correctness of the command prior to transmission. A buddy system should be used for manning the command console.