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I am having a problem with designing the On Board Data Handling (OBDH) system for our MSI (Multi-Spectral Imager) payload. Our payload will be detached from Orbiter and it will take photos (for chemical characterization of the surface of Enceladus) on its re-entry/descend phase (~ 2hour). So, I need to take photos as much as possible within this time period and need to send back data to the carrier and then the carrier will send those back to the orbiter. It's a disposable unit, so it will destroy by the time it'll touch the surface.

I am now considering for myself the following questions

  1. What could be the complete internal architecture of my payload's OBDH system?
  2. Which processor should I use for fast processing, less power budget?
  3. What could be the microcontroller? How much should I have (at least) data storage Flash, RAM, ROM?
  4. Would it be better to use FPGA?

and I'd like to ask how to approach them.

Question: What are the tradeoffs I need to consider in order to address these questions about OBDH system design for the Multi-Spectral Imager payload described above?

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    $\begingroup$ What exactly are you trying to accomplish? You could use a Raspberry Pi hooked up to a camera module handle the transmission and capturing of those photos. $\endgroup$
    – user96931
    May 21, 2019 at 16:46
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    $\begingroup$ Hi, we are trying to throw some small disposable unit from the orbiter to characterize the landing site location and chemical characterization of that point. So, while it will be on its descent trajectory our payload will start taking photos and send it back to the orbiter, only on its descent phase before crashing at the ground. And we will be using the pushbroom technique for optical sys so there will be a rotating mirror which can also be controlled by OBC. So, I need fast data transfer and processor and image compression. I want to know the best inside architecture design for OBC? $\endgroup$
    – JOY
    May 21, 2019 at 21:35
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    $\begingroup$ I've adjusted your question, have a look and feel free to edit further. Your most recent edit was very helpful but then left the question way too broad for Stack Exchange. Here it's necessary to ask a specific question that can be answered objectively (i.e. without a lot of opinion) and in a reasonably small amount of space. Rather than ask for the best design (which would be closed as too broad or primarily opinion-based) It now asks for tradeoffs which can lead to a more objective answer. $\endgroup$
    – uhoh
    May 22, 2019 at 0:05
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    $\begingroup$ You may also want to consider doing this as a series of smaller questions. You can ask as many good questions as you like, but if they are related it's better to wait for some feedback or answers on one before asking the next, and include links to previous questions when relevant. Welcome to Space! $\endgroup$
    – uhoh
    May 22, 2019 at 0:06
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    $\begingroup$ @uhoh Thank you so much, I was not sure how to put this question because I have got puzzled in one position with my project. Yes, exactly for trade-off analysis. Although I need to care about MIPS, frame rate of my payload. Thank you. $\endgroup$
    – JOY
    May 22, 2019 at 7:56

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What could be the complete internal architecture of my payload's OBDH system?

I would use a Raspberry Pi model 3b+, connected to a camera module. You may run the latest version of Raspbian (a Linux flavor based on Debian) and configure the startup scripts to start streaming footage.

Which processor should I use for fast processing, less power budget?

The Raspberry Pi 3 B+, with HDMI and LEDs off using WiFi clocks in at 400 mA (2.0W), and has a quad-core A53 (ARMv8) 64-bit @ 1.4GHz processor as well as 1GB RAM. If this is too much, you may use a Raspberry Pi Zero W (W for wireless) which, with HDMI and LEDs off, clocks in at 120 mA (0.7W), and has a ARM11 @ 1GHz as well as 512MB RAM. However, if possible I reccomend using the 3 B+ due to its superior power and RAM. You may use this to power it, and it lasted 15 hours on a Raspberry Pi continuously being pinged over wifi. For a full chart of Raspberry Pi energy consumption by model, visit here.

What could be the microcontroller? How much should I have (at least) data storage Flash, RAM, ROM?

Both of the above said configurations would fully support live-streaming using the camera module and WiFi. If you plan to save footage on a disk, you may use a 64gb MicroSD card for either the 3 B+ or the Zero.

Would it be better to use FPGA?

If you have the technical knowledge, you could consider it, however I reccomend using the above.

Lastly, Dave Akerman has launched a RPi into near-space and you may gain insight into this from what he did. The Raspberry Pi has a great support community at Raspberry Pi StackExchange where I myself help people out. Also, please document your project in a blog. We all would love to hear about it!

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