I’m putting this in GQ and not CS because I’m not interested in the technobabble that the series writers have come up with what they are and what they do over the years. What I want to know is if we were going to equip a spaceship with sensors what would they have? Obviously you’d want various radiation detectors and radar, but what else would there be?
It depends on where you are going, and whether it’s just a cargo spacecraft or an exploration. For navigating in the solar system you’d probably want:
[ul]
[li]Inertial sensors (gyroscope and acceleration sensors)[/li][li]Sun sensor and star trackers (for calibrating gyroscopes)[/li][li]Radar[/li][li]Communication (to get data from other people’s sensors, esp. those on earth)[/li][/ul]
And to insure safety of crew, you’d want X-ray and particle detectors. If it’s a exploration, you’d of course want a complete set of remote sensing equipment. That means imagers and spectrometers in all wavelengths from radio to X-rays, magnetometer, particle detectors of all types, and probes equipped for closeup and in-situ measurements of chemical composition.
Although this is not a sensor, you better not forget to include a death ray - I think they are called phasers these days.
You and scr4 pretty much covered the EM band… there’s not much left to sense! I think the only stuff we wouldn’t include would be things like neutrino detectors (they’re too massive) and tachyon detectors (they don’t exist. :D).
Your average digital camera of today can perform a significant fraction of what the Voyager probes did in the 70’s, so I don’t see any energy/space/weight problems preventing the addition of kitchen-sink style detection to future spacecraft.
Heh. And while b&i thinks he’s being silly, I’ll second the motion for some type of laser. Nothing like a 1920’s style death ray to chip off a chunk of comet for long range speculation.
OK, so maybe I made too broad a sweep. 
To be more specific and realistic, I’d say:
[ul]
[li]Synthetic aperture radar for mapping surface features (used on the Magellan spacecraft, among others)[/li][li]Optical and infrared imaging telescopes[/li][li]Optical spectrometer for analyzing surface (and atmosphere, if any) composition remotely[/li][li]Charged particle sensors for observing the solar wind and its interaction with your planet/astreoid[/li][li]Probes equipped for X-ray fluorescence measurements, or just sample retrieval (to be analyzed in the lab on your spacecraft)[/li][/ul]
Actually I’m not sure how useful UV and X-ray would be, apart from fluorescence measurements (bombarding a sample with X-rays or other particles and causing the sample to emit characteristic X-rays). If you were visiting another star though, you’d definitely want X-ray telescopes to observe the star.
By the way Nanoda, you left gravitational wave detectors. They do exist and aren’t as heavy as neutrino detectors, but I don’t see the point of taking one with you on a spacecraft.
There’s a very good reason that most of our spaceborne sensors are passive, and our best active sensors are stationary or ship-based: active is heavy and uses lots of power.
I would like to humbly suggest that you design a pretty serious set of passive arrays, and spend very little of your budget adding active sensors. If you’re going to be traveling at interstellar distances, it’s going to get really dark out, and even if you do have fusion power, the kind of ranges you’re going to be doing most of your work in make sending out radiation a long-term project.
If you put a fully capable passive sensor array at each extreme end of your ship, you gain redundancy as well as the ability to triangulate. If you think you’re more likely to want to look straight ahead (instead of broadside) then either mount them at the extreme left and right or top and bottom of your ship, or use reaction wheels to rotate your ship through one full turn as you approach the target. The triangulation would allow you to make binocular images in any of the bands you’re interested in.
Once you’ve characterized the distance between the sensor arrays and the motion of the spacecraft, a pair of passive arrays are probably going to be more useful than an active sensor.
I’m not saying “don’t bring any active sensors” – I’m just saying keep them tucked away for when you’re up close to something and really want to probe the hell out of it.
Forward Mass detectors sound like useful bits of kit, although I can’t find much information on the range and sensitivity of these in real life.
Anyone got a good link so’s I can update our SF sensor pages
here and [http://www.orionsarm.com/ships/sensors.html]here?
Well, scr4 pretty much covered the range of remote sensing instrumentation used today by spacecraft. I would add lidar for debris detection, and perhaps hi-res imaging of small targets, since powerful solid state laser technology is maturing quickly nowadays.
Another maturing technology is terahertz wave spectrometery, but it hasn’t quite rounded the bend yet. I saw the first paper on THz radiation in a SPIE proceedings about 15 years ago, and just this week saw the first demonstration of what may be a practical application in about 5 more years.
On the other side of the spectrum, I work on hyperspectral imaging sensors, which make images with spectral resolutions approaching 0.25nm. The result is a data “cube” with a seperate image for each ultra-thin color “slice.” Instruments like this are the first ones capable of the kind of feats that Spock and Sulu depict, quickly locating and distinguishing species on the ground from orbit, and making chemical analyses of the atmosphere, spotting localized concentrations of trace components.
However, you still need expert software and operators to do this, and here is where the technology is outpacing our expertise. We can make sensors that produce Gigabytes of data per image, but the users (scientists) don’t know what to do with all that data yet. We have trouble selling these sensors because of it. Everyone agrees this kind of instrument is useful, but right now, we’re still learning how to make use of them.
Right now, the best technique is to pick the “slices” that seem to be the “most different” and plot them in an N-dimensional space, one axis for each slice. Then twist and turn the N-dimensional object and look for the “pointy bits.” It’s hard to explain even in jargon, much less layman’s terms. The software for this is still only suited for operation by highly-trained specialists. It would be possible for an astronaut to operate this, but he would need to be a scientist, not a pilot (i.e., a mission specialist).
For more info on hyperspectral imaging, look here.
To clarify, it’s the detectors which are massive, not the neutrinos. But depending on your design, you can use water for most of your detector mass, so for a well-populated ship with a large resevoir of reserve water, you might want to go ahead and put a few photomultiplier tubes in your tank to make a neutrino detector. A neutrino detector would be of limited usefulness for exploring uninhabited worlds, but of great value if you think you might meet anything intelligent: A nuclear reactor will show up easily on a neutrino detector, which would let you roughly gauge the technology level of the civilizations you meet.
I can’t imagine what use a gravitational wave detector would be, but they’re cheap enough (once you have easy access to space, which a starship presumes) that you might as well bring one along. It can’t hurt, and if nothing else, you could triangulate with Earthly gravitational wave detectors to find distances to sources.
While we’re at it, differential gravitometers would also be useful, for detecting masses. And along the same lines, magnetometers and electrometers.
And further while we’re at it, we’ll want clones of the Hubble, MAP, Chandra, Webb, Hipparcos, Compton, and pretty much every other science satellite or probe we’ve ever launched or will launch. All of them added together would still be much less massive than a full-blown starship. These are all in essence telescopes; spectrometers of variious sorts are common instruments to use with a telescope.
For active sensors, I don’t think that anything but radar or lidar has long enough range to be interesting. We’ll surely have things like MRIs aboard, but in the labs, for analyzing samples brought on board.
Do you think it would be a good idea to bring along a “whisker”? A small, unmanned probe with its own drive that could fly out if you wanted good interferometry. It could act as an external sensor for inspecting your hull, too.
Something that occured to me in reading over this thread is that a laser might come in handy for taking temperature readings of specific points on objects. IRRC, thermal imaging is good for giving one an overall picture of how warm something is, but if you’re trying to pin down the temp at a specific point in the object, you hit it with a laser. (I know that the fairly inexpensive models are set up like this. It might be because it’s cheaper to do it that way than to use a better thermal imaging unit.)
Chronos, what about the reactor on the ship carrying the neutrino detector? Obviously it would be impossible to shield your reactor enough to prevent the neutrinos from escaping, so could you expect your reactor to emit a certain amount of neutrinos at all times? Otherwise, I’d think that you’d have a hard time telling if it was your reactor or someone elses causing the sudden spike in neutrinos.
One way to detect dust and dim objects in a volume of space involves a small moon and a large nuclear device;
detonate the device behind the moon from your point of view and you will get a flashbulb type snapshot of all the material in the immediate area;
when you think about it, any active sensor would need to use a similar amount of energy to get an image of similar resolution tothat given by a flashbulb-nuke device.
(originally proposed by Arthur Clarke, I believe).
I’m posting this link to give an idea of some of the sensors and sampling equipment that will be expected to be carried on a ship in the Interplanetary age; these X-project people are planning it for real over at JPL and Arizona ; I just hope they get the money one day.
http://www.lpl.arizona.edu/grad/teamX/missions/
extracted from this website;
Sensors and other equipment; (some categories may overlap)
Hi res Cameras with multiple filter options
Near-and Thermal-infrared imager
laser altimeter
Gamma ray spectrometer
Panoramic/stereoscopic cameras
Mini Thermal Emission Spectrometer
Visible and Infrared Mapping Spectrometer (VIMS)
Mossbauer spectrometer
Microscopic imager
Rock abrasion tool
APXS alpha particle X-ray spectrometer
imaging spectrometer/spectrographs for UV, visual, IR, and thermal IR
mass spectrometer
Visible, near and thermal IR spectrometry
gas chromatograph
Sample return and analysis;
MVACS package; developed for use on mars, it includes meteorological equipment, stereo imaging equipment and a TEGA thermal and evolved gas analyser;
imager/radar system to detect small asteroids (meteoroids)
seismic probes and penetrators/seismic net
Sample Collection/Water Detection Experiment
Soil Thermal Experiment
Atmospheric Descent Accelerometer
Impact Accelerometer
magnetometer, coils and electrodes for
electromagnetic sounding
gravitometer
Radio science instruments
Radar mapping equipment
steroscopic mapping cameras
dust detectors
Plume sampler
What kind of sensor would one need if one wanted to test for the presence of molecular oxygen from orbit, or from even fom beyond the star system.
I ask this because life is the only known method of natural large scale oxygen production.
A spectrometer. IIRC, Cassini did this on it’s swing by earth.
Re: triangulation - Unless your ship is really big and the equipment really small and cheap, I think you’re unlikely to want to do that. Much easier to wait a while while the ship moves, then capture a 2nd set of data.