Scientific Space Instrument Design

[nanila]

[Block diagram of a "generic" space instrument.]

I'm giving a talk next week* and I needed a block diagram of a generic spacecraft instrument. I made one many moons ago but it looks verry dated now and is also about 400x300 pixels and I can't find the original graphics program file. So I thought, I'll make myself a new one.

I'll probably talk about the slide it's on for a minute and a half, maybe two. I probably shouldn't have spent two hours on this. I'm now trying to justify the time spent to myself by sharing it with the internet. Hi, internet!

If you're wondering what this is, it shows how a set of sensors that measure physical parameters in space (on the right in green, labeled MAGOBS and MAGIBS) are connected to a spacecraft (on the left in gold). The physical parameter, in the case of these two sensors, is the ambient magnetic field.

The FEEs transform the physical parameters measured by the sensors into electrical signals.

The ICU is the instrument control unit, which takes telecommands (TCs) and timing signals from the spacecraft and passes them to the sensors. It also takes the data passed back from the front-end electronics (FEEs) and turns it into nice telemetry packets (TMs) that the spacecraft can then package up and beam to Earth through its communications system.

The PCU is the power converter unit, which takes the standard voltage from the spacecraft (usually +28 Volts) and chops it up into secondary voltages that the instrument FEEs can use (e.g. +/- 1.5 Volts)

It all looks very simple, no? You wouldn't think this sort of thing would take a dozen years or so to implement and launch would you? Sadly, you would be wrong about that.

* And two the week after that. They are all different. Whyyyy did I think it would be a good idea to sign up to give a group meeting when I already knew I had another two talks to give? /o\

Comments

[quoththeravyn]

There's a lot of stuff in the boxes, of course.

My task for the last year? Or so? (eyeroll) has been to upgrade a thermal model for our PCU-equivalent box, which operates in a vacuum (of course) so it's... challenging. In particular because we turned on another heater a couple months *after* I calibrated the model.

[nanila]

It's the stuff in the boxes that takes all the time, yep.

Although I guess I shouldn't underestimate the arrows, either. Certainly the ones between MAGOBS/MAGIBS and their FEEs involve some loooong harnesses.

Thermal modeling is a Dark Art. I bow in deep respect of your powers.

[hilarita]

Strictly, it's a block diagram of products and data flow.*

We've managed to spend several hours today coming up with a diagram that looks quite like a diagram to receive and process data from space satellites/craft (i.e. the earth end of the downlink from a spacecraft such as you describe), only with different labels on it.**


* Brought to you by spending 20 minutes in discussion before putting the words 'strawman functional block diagram' at the top of a diagram.

** There were some different bits that looked less like that, but maybe we can change the labels and STFC can use it for a space project.

[nanila]

It's so odd hearing "strawman" used in a scientific/technical argument. Just because it's nearly always pejorative in other contexts.

[lark_ascends]

*hugs you hard*

[nanila]

*hugs back* Thank you. The group meeting went well. The other two talks are next week; one is done (the first one, chronologically, huzzah) and the other getting there.