Communication and Navigation for space flight on Europa

Question

Considering the rather hostile radiation environment on Europa, what communication and navigation systems might be used with near-future manned spacecraft? What would the ranges and features of this equipment be?

I would be most interested to hear about the possible functionality of existing systems, such as VOR/DME, UHF/VHF radio comms, radar altimeters, or similar equivalents which a budding colony may distribute around the surface. Let's not assume the existence of a well-established GPS constellation nor availability of relay satellites, it is early days for my colony. My spacecraft will be orbital and suborbital short/medium-range transport craft, hopping from one outpost to another.

I have been struggling with documents like this: http://www.people.virginia.edu/~rej/papers09/Paranicas4003.pdf but it's a bit too much info for me. Are there low radiation areas or periodic low points which would be preferred for piloting activities?

What radiation monitors would be used on the space craft, and what are the most meaningful variables to present to the pilot?

Answers should work towards a Europa version of present day aircraft and Apollo-era spacecraft where possible. No subspace relays etc. If computers can be avoided or even explained away then that's great.

I'm not worried about the pilot radiation dose, lets assume an adequate level of shielding on the pilot and vehicle electronics. A good answer will provide a brief summary of the radiation environment as it pertains to space flight, radiation environment "weather" patterns, with focus on the impact of such radiation on the piloting spacecraft, radio signal reception, quality and range... factors like that.

Answer 1

What radiation monitors would be used on the space craft, and what are the most meaningful variables to present to the pilot?

This is an electronic personal dosimeter (EPD). Anyone working in a radiation enviornment would be wearing one. The medical branch of controlling organization for your Europa explorers will determine a desired maximum daily (or yearly) dose. For example, the NRC establishes dose limits for nuclear workers. Your EPD will be set such that it alarms if you are getting radiated at a rate that puts you in danger of exceeding your daily dose.

If you want to avoid computers (the EPD is one), then the older self-indicating pocket dosimiter (SIPD) is a device that holds a charge that depletes as exposed to radiation. This won't alarm, but the pilot can look at it at any time to determine his dose. I couldn't find any actual products for sale, but here is the wiki page.

A more advanced system would be built into any vehicle with humans or complex electronics. Many of the functions of currently existing environmental monitoring would not be needed, such as air particulate, beta, and alpha detection. Gamma detectors are great, but a generally unidirectional. In a heavy radiation environment like Europa, some engineering work would have to be put into an integrated gamma monitor that senses radiation from all directions. I'm not sure anything like that exists right now, since there is little need.

Are there low radiation areas or periodic low points which would be preferred for piloting activities?

According to your paper:

• The atmosphere of Europa, tenuous as it is, does not provide any protection from radiation.
• Electrons with energies in the MeV range (i.e. very dangerous) are lower than peak but still substantial in Europa's orbit. MeV protons (even more dangerous) are rare.
• Europa's orbit is 10$^\circ$ off of the disk of Jupiter's magnetic field (the magnetic field is titled from Jupiter's spin axis; Europa is only 0.466$$\circ$ off Jupiter's equator), so when Europa is at higher north or south magnetic latitudes, the prevalence of energetic particles is reduced. No magnitude is given for this effect, though presumably the period is equal to Europa's orbital period.
• Because Jupiter's background radiation is so high, 'injections' (not further defined, but other papers suggest due to changes in solar wind) provide little more than background noise in the radiation levels.
• For some low energy ions, magnetic effects heavily favor bombardment of the planet's surface in the trailing hemisphere. For other higher energy ions bombardment is even. Electron energy flux is given in Figure 7 showing about an order of magnitude decrease from equator to poles. In summary (this is the part you want) Fig 8 shows that the trailing edge, equator receives an order of magnitude greater radiation than the leading hemisphere at the equator.
• Figs 9 and 10 show that dose rate drops by 6 orders of magnitude after 1 meter of ice.

TL;DR: Relatively little variation over time, trailing hemisphere get 10x radiation of leading hemisphere.

What communication and navigation systems might be used with near-future manned spacecraft? What would the ranges and features of this equipment be?

The Galileo probe spent 14 years in space, and 8 in the Jovian system, so its equipment is a good benchmark.

Navigation is most easily done by triangulating position from beacons. One of these beacons could easily be beaned into space from earth. Other beacons would either be man-made installations around the solar system (lets call this SPS - Solar system Positioning System) or by using astronomical phenomena (I talk about using pulsars with some links to papers here). An onboard computer would have to be no more advanced than your average Garmin.

Galileo talked back and forth to earth on S-band (2.295 GHz) using the Deep Space Network of radio dishes around the world. Manned exploration of the outer solar system would probably incentivize putting these dishes in near-Earth space for better reception and bandwidth. I might point out that 100% of Galileo's recorded data was successfully returned to Earth, so you won't evidently have many communications problems on S-band. If you don't have any comms problems in this band, you could use S-band also for radars, altimiters, local navigation beacons, etc. Alternately, survey teams would surely determine the best and least-interfered with frequencies for all this equipment. I doubt that EM disruption of navigation and comms equipment would be limiting.

To support both of those systems, onboard computers can be made with silicon-on-sapphire integrated circuits. These are resistant to radiation and would probably be used extensively on any space vehicles operating in the inner Jovian system with high background radiation. Incidentally, these computers won't have the circuit density of your iPhone since not as much design research has been put into miniaturizing them; as a result this will partially achieve your anti-computer goals by making spacecraft computers larger and slower compared to earth computers.

Answer 2

Musk's space ships attempt to cut costs from regular spaceships by having redundant computer systems perform calculations, and using the calculation that at least two out of three agree with. Current computer processors for space satellites are like RAD750, and cost hundreds of thousands of dollars. However it's possible that the radiation levels are high enough that one would need redundant RAD750 processors, Pioneers 10 and 11 did have electronics fail. Juno's electronics are shielded in a 0.3 inch titanium vault.

It is possible to approach Jupiter through it's magnetotail, a low energy region of Jupiter's magnetosphere directed away from the sun, such an approach would be indirect and will take longer.

If you want things to be more complicated for the pilot... space travel is pretty automated now, requiring precision far higher than the human hand can provide, and through calculations made long before the journey begins.

Radio frequency would work the same as on Earth. There are radio storms at frequencies you don't have to use though.

Sure you can't try for Ganymede or Callisto?