Week 5 - Command & Data Handling + Lab

Submitted by j.akagi on Tue, 01/26/2010 - 11:08am

Discussion began with students learning some fundamental responsibilities of the CDH subsystem, as well as some qualities of an optimal CDH subsystem. Students briefly read about some design methods for the CDH subsystems of past UH SmallSat projects. For the sake of comparison, students were then shown pictures of some of the hardware used for the CDH subsystems of large and small satellite systems, before interacting with that of the EyasSat.

Lab began with students first familiarizing themselves with the CDH subsystem of the EyasSat, considering both its block diagram, as well as a figure which listed several of its key components. Students then completed a sequence of hands-on steps involving the CDH subsystem. These steps included integrating it with the EPS, confirming several of its software functionality tests, and observing its capability to measure different values (such as temperatures) throughout the subsystem.

 

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Groups:
11 Mar00:30

James' group: Elizabeth, Pamela, Philip

By ptoshi

Problem 1: What two types of data could the CDH collect and monitor for housekeeping?

Answer: Two important types of data that the CDH should collect and monitor are temperature and power/energy levels. Temperature monitoring is important because it determines whether everything is functioning properly; abnormal temperature readings mean that something is malfunctioning and steps should be taken to reduce the temperature and prevent the entire satellite from breaking down. Power needs to me monitored to ensure that all subsystems in the satellite have enough power to function properly. Temperature and power readings are interconnected, as too much power to one subsystem could result in an abnormal temperature.

Problem 2: Why is validation and decoding of data important?

Answer: Data validation is important to know if the subsystem you’re talking to received its command so you can decide if you should send another command or resend the old command. This is important because the subsystem may still be in the middle of a task and can't receive any new data until it finishes the task. It might cause everything to go out of sync if the CDH thinks something was sent when it wasn’t and decides to move tell another subsystem to use data that wasn’t updated. Decoding is important because coding allows you to make commands more compact and if you don't decode it correctly, you may end up talking to the wrong device or you may execute the wrong task which would cause malfunctions.

08 Mar23:13

John's Group Question 1 & 2

By Alex Gao

John's Group: Matthew, Alex

Problem 1: What kind of data from a CDH would be important in keeping a satellite functioning normally?

Answer: One type of data that would be extremely important to collect and monitor would be temperature readings from different components and areas of the satellite.  Abnormal temperature readings could be the first sign of a malfunction subsystem or component, or dangerous environmental conditions.  For example, a component might be taking in too much power due to a problem with the EPS.  Temperature readings can help in identifying and diagnosing problems. Similarly, data about the satellite’s current power (voltage & current) could also help in identifying potential problems with any of the satellite’s components.  Power readings could also help in keeping track of other information such as the degradation of the satellites batteries.  Power data can also be compared with temperature data in the case of any anomalous readings or problems. 

Problem 2: Why is it so important for a satellite to be able to decode and validate commands?

Answer: Validating and decoding commands is very important because failing to do so could cause catastrophic results.  For example, if the satellite is in perfect working order, except for its ability to validate and decode commands, it will be able to process whatever commands it receives with no problems, but with faulty decoding/validating, those might be completely wrong commands.  It will do what it is told to do.  It cannot judge for itself what commands are right or wrong, and is very capable of damaging itself with faulty commands.  Commands tell what the satellite to do; Without them, the satellite would be quite useless.    

08 Mar14:40

Wei-Hann's Group: Dana and John

By jfurumo

 

Problem 1:     One of the common duties of CDH is housekeeping where CDH gathers, formats, and processes the overall status of the spacecraft. What are two types of data monitored in this housekeeping, and what is their importance?
 
Two types of data monitored in this housekeeping are system temperature and power level. The importance of running routine checks on temperature is to ensure systems are maintaining safe operating temperatures. If the system were to become overheated, a step could be taken to reduce temperature before system failure. The importance of monitoring power is to ensure systems are running and that there is enough power to distribute respectively to subsystems and run their components. Too much power can damage components, and too little will render them useless. Successful satellite operation involves the integration of several systems. If one link in the chain fails, the whole chain fails. Regular "housekeeping" is necessary to make sure each link is functioning properly.
 
Problem 2:     A major function of CDH is that it receives, validates, decodes, and distributes commands. This is a specific description of tasks, and a lot of emphasis is placed on validation and decoding after the message is received. Why are these two tasks so important? 
 
The primary function of the CDH is to receive and distribute commands. This entails collecting data and signals from other components and then running software that directs it to perform certain duties as a result. In this way, the CDH is akin to the brain of the satellite. In order to acheive this goal, the CDH must decode and validate data. Decoding is important because if the data were written in an unreadable format, collecting it would be of no value because it wouldn’t suit its purpose, which is to provide system-running conditions to the observing engineers. If we can decode the message, will then be able to determine if its message is valid. Validation is important because data must be in acceptable ranges. If data is not valid, the CDH would disregard this data. For example, if a system is supposed to return a value of '1' for operating condition and '0' for non-operating condition, and the system returned a value of '2' then the CDH would know through validation that this input is not valid and would disregard it and check again.