summary
Sending analog audio signals a few meters over shielded coax cable is a solved problem.
If your signals are limited to 3200Hz and you need 8 or 10 bits of precision per sample, then I would be pretty comfortable using standard audio coax cable to send the raw analog signals.
That might be the lowest-cost, lowest-battery-power way to handle things.
If you require DC-accurate readings at 3200Hz and 20 or 24 bits of precision per sample, shipping analog signals over even 2 meters of cable is basically impossible at any price.
If you need that precision, you are forced to digitize the signals right at the source, and ship them over the cables in some digital format.
details
Transmitting in digital format generally requires one to spend a little more money on electronics at each sensor, but it allows you to save a little money on lower-cost UTP cables and low-cost connectors.
In a few cases, transmitting in a digital format lets you use fewer cables -- a single daisy-chain through each sensor ending at the host, where each sensor forwards data from the "upstream" sensors "downstream" towards the host computer, as well as sending its own data "downstream" towards the host computer on the same cable. With an analog system, you are pretty much forced to run an independent wire to each sensor -- analog multiplexing techniques end up costing more than digital multiplexing techniques.
As the bandwidth goes up, or the desired precision of the signals goes up, or both, analog cables need more and more shielding (i.e., get more expensive) to block outside interference and cross-interference.
Eventually you reach a point where it's basically impossible to put enough shielding on a cable to get the desired bandwidth and precision.
Suggestion
Post a new question something like "I have a bunch of (insert name here) digital sensors that I want to distribute over a large area of a few meters, but I don't want to run dozens of digital control wires per sensor back to my host MCU. What's a reasonably low-cost, low-energy digital circuit I can put to reduce the number of wires I need to run to each sensor? I might be willing to run a full 4-pair CAT5 cable to each sensor to carry power + data, but no more!
Ideally much less -- is it possible to share one 4-pair CAT5 cable among 2 or 3 sensors to carry power + data?"
If you are willing to spend a few extra bucks on digital chips in order to avoid the hassle of programming a MCU at each remote location, please specify "without a MCU" (like How to decode morse code with digital logic ).
It's possible the resulting circuit may give you the full precision available from your (insert name here) digital sensors, but have a net cost less than an analog-signal system, when you balance the extra digital electronics and the low-cost unshielded cables and connectors vs. the lower analog electronics cost and the higher shielded cables and connectors.
Best Answer
Either approach might be alright: analog point-to-point connection (down to, say, 10 or 12 bits of resolution), or I2C. CubeSats are small. They operate far from external sources of EMI. If the switch-mode power supplies in the EPS (electric power subsystem) are properly designed, they should not generate much EMI.
Is it likely that the payload will generate EMI?
From systems engineering standpoint, both point-to-point and bus have their pros and cons.
The pro of point-to-point is that it's simple (in the k.i.s.s. way). The con is that it doesn't scale as well as I2C.
The pro of the I2C is that it scales well, and it's convenient. The con is that complexity increases. The bus can also be a single point of failure: I2C bus can get stuck.
If you have more than one sensor on that board, and they lend themselves to an A/D connected via I2C. Or, if you anticipate that there may be more sensors on that board in the future. Then I2C might be convenient.
p.s. In school, I have designed a C&DH board for the MAST CubeSat. It had an extensive I2C bus, which worked without a hitch.
Later, I have designed and then had to grapple with an overgrown [because of lack of a better upfront judgement] I2C bus in an industrial instrument.