Tag: space

The Europa Lander mission

In the space exploration world many are excited by the possibilities of a robotic mission to the distant moon of Europa for scientific investigation. The mission plan from NASA is titled ‘Europa Clipper’ and it’s promo page can be found here: https://www.nasa.gov/europa.

The scientific merits of such an expedition need not be repeated, and are well explained enough on the main site, so instead I’ll focus on offering a layman’s explanation of the intriguing technical aspects in the press release.

Of special note is the instrument payload:

“The spacecraft’s science instruments will measure the depth of the ice crust, measure the depth of the internal ocean and how thick and salty it is, capture color images of surface geology in detail, and analyze potential plumes.”

i.e. it will utilize novel techniques and technologies in order to accomplish something never before attempted on another body in the solar system.

“Scientists are especially interested in what makes up the moon’s surface. Evidence suggests that material exposed there has been mixed through the icy crust and perhaps comes from the ocean beneath.”

i.e. There is a likely probability of very astonishing discoveries akin to the unexpected images returned by the New Horizons probe.

“Europa Clipper will also investigate the moon’s gravity field, which will tell scientists more about both how the moon flexes as Jupiter pulls on it and how that action could potentially warm the internal ocean.”

i.e. Many alternative usages both forseen, and unforseen, are planned for the mission payload. This could very well be a very long lasting mission, akin to the Spirit and Opportunity Mars rovers, far exceeding it’s nominal projected lifespan.

““We’re doing work that a decade from now will change how we think about the diversity of worlds in the outer solar system – and about where life might be able to exist right now, not in the distant past,” said Europa Clipper Project Scientist Robert Pappalardo of JPL.”

i.e. This is more than an academic and curiosity satisfication exercise, there will likely be practical consequences to the future evolution of scientific effort, space exploration effort, biological efforts, and long term planning of future missions.

“But the more instruments a spacecraft carries, the more they interact and potentially affect each other’s operation. To that end, noted Pappalardo, “We’re currently making sure the instruments can all operate at the same time without electromagnetic interference.””

i.e. The instruments will be the most shielded and hardened yet to electromagnetic interference, excluding the solar probes.

“Missions such as Europa Clipper help contribute to the field of astrobiology, the interdisciplinary research on the variables and conditions of distant worlds that could harbor life as we know it. While Europa Clipper is not a life-detection mission, it will conduct detailed reconnaissance of Europa and investigate whether the icy moon, with its subsurface ocean, has the capability to support life. Understanding Europa’s habitability will help scientists better understand how life developed on Earth and the potential for finding life beyond our planet.”

i.e. If the mission proves successful there will be many productive papers and stimulation for future researchers. In addition, a presently distant dream, of an alien life detection mission, will be that much closer to fruition depending on what is discovered.

The UN Security Council as the final arbiter for Outer Space claims

As the United Nations Security Council (UNSC) already serves as the final arbiter, and ultimate enforcer, of all claims in international waters it would be natural to suppose that claims above the Karman Line, i.e. outer space, could be settled in a likewise fashion.

The need becomes more prominent every year due to the unique characteristics of the environment where there are no fixed boundaries and where one rogue actor can severely damage and impair the activites of everyone else. A prominent example is the possibility of ‘Kessler syndrome’, arising from fundamental orbital dynamics, that could create irreversible consequences vastly greater than the initial effect.

As the importance of maintaining the outer space environment from deleterious effects grows exponentially with every new object introduced, the danger of not having a central dispute resolution mechanism likewise grows exponentially. Therefore, even with just the issue of keeping orbits safe, there will clearly be a tipping point where the need for global coordination becomes of paramount importance.

Indeed as competing interests will undoubtedly also grow in outer space the need for a central coordinating body will probably expand to cover all disputable outer space activities that cannot be resolved bilaterally.

Due to the rapid nature of such growth and as there is not presently, nor in the forseeable future, any other organization that can credibly maintain itself to be the final arbiter over the whole Earth, that responsibility will by default fall on the UNSC. Specifically, given the current structure, some kind of subcommittee or judicial body for outer space affairs seems most probable.

Although my personal leanings are towards a freer environmemt with less paperwork, the unforgiving p challenges of the laws of physics in outer space are unavoidable and will have to be addressed for the future benefit of civilization.

Last edited April 1, 2021

If I were empowered to make decisions, as fair as possible, for the entire Earth…

I would first set up shop with a random number generator based off distant cosmic rays and a sufficiently powerful telescope in a secure, but verifiable by everyone else, enviroment.

Then I would let it pick a random star, any star, out in the cosmos.

Then I would decide all proposals on this planet based on how accurately, precisely, and completely they predict future observations of said star. If this policy is ever deviated from, everyone also equipped with eyes and measuring instruments will also know and can thus pick someone else to listen to.

With all disputable parameters, such as the interval between each observation, also picked randomly by cosmic rays and announced at a predetermined time.

There will be no upper or lower limit to the number of logical steps acceptable for said predictions. Nor will there be any limit to the scope or content of claims. Nor any other restriction that could not be resolved through better observational predictions.

If there is no credible way to link the claim with stellar observations, or if current technology does not render the precision and accuracy feasible, I would delegate the decision to subordinate decision making authorities with a provisional status, until technology and reason and so on advance to a sufficient stage in the future.

The results, with all intermediary information, will also be published and disseminated to everyone, at predetermined intervals, with every disputable factor decided by the random influx of cosmic rays. And again if there is a majority consensus in whatever direction contrary, they can then select who is most trustworthy from amongst themselves.

If the limits for a single star are exhausted then another one will be selected at random and so on.

Therefore, all possible considerations, all possible interest groups, all speculations in general, will be treated as equitably as possible, at least until we run out of stars to look at. And at that future age I’m confident some even greater methods will yet be devised!

Capturing the Earth, satellite imagery storage requirements at planetary scale

Coming across the capacities of the very large data centres now being built, in the exabyte range, it’s interesting to consider how much space is needed to store an image of the entire earth captured at the highest possible resolutions, with current technology, from a realistic orbit.

There currently exists databases of partial imagery of the earth in near real time, through composite stitching of various satellite outputs, providers such as Zoom.Earth have already achieved quite a bit in this field.

What if one day something akin to that is available with the most advanced imagery? The current state of the art for the top secret satellites is likely under 10 cm, though of course the exact number is classified. I firmly believe in the near future 5 cm resolution will be routinely available with advancements in optics.

Rough numbers:

1 square km at 5 cm resolution = 20000 x 2000 pixel image = 400 megapixels

In 30 bit RGB (10 bit color) that is 1.5 GB losslessly compressed (2 to 1 compression) ideally.

Earth has a surface area of 510 000 000 square km

That’s a 204 quadrillion pixel image!

Some simple math gives 765 petabytes (PB) of storage is needed for one image. Where 1 PB = 1000 TB = 1 million GB = 1 billion MB

Of course in reality the earth is not perfectly spherical, additional overhead data has to be stored, 765 PB would require redundant storage or you would lose that to bit rot quite quickly, the water images could probably be compressed more, etc.

Given that roughly 71% of the surface area is water a few hundred PB could probably be cut through lossy compression without sacrificing any perceptible image quality.

Nonetheless let’s assume minimal data overhead and complete accuracy, so we’ll need triple redundancy, at least!, with some buffer as well.

A ballpark number could 2400 PB, or 2.4 exabytes, of actual disk space needed for one image.

If you could accept the odd bit flip or compression artifact this could easily be reduced to 240 PB given the advanced state of compression algorithms nowadays.

So what about video?

At 30 fps at lossless quality that gives 72 exabytes (EB) per second of video!

At a more realistic compressed standard, perhaps as little as 1.44 EB per second, assuming 100 to 1 lossy compression efficiency.

This calculation is a bit silly as the only we have currently of capturing whole earth shots is with satellites parked at geostationary orbit, that could not reach a 5cm resolution without some truly massive optics. I really don’t expect to see this sort of capability this century.

A more realistic way is to look at what the reasonable capabilities are of geostationary orbit (GEO) earth observation satellites within the foreseeable future, with say Hubble sized optics. Although the current state of the art is at 500 meters with Japan’s Himawari 8, I believe one day we can achieve 10 meter resolution imagery from GEO.

At the 10 meter per pixel scale, that gives 1.8 PB per second of video at 2:1 lossless quality, and just 36 TB per second at 100 to 1 lossy compression. Actually feasible with current storage technologies.

Although 10 meters per pixel will barely resolve buildings, this is still quite useful for at least studying cloud formations, weather patterns, ship movements, and perhaps large plane movements at a massively improved resolution from current weather satellites.

The trickiest part would be imaging the poles since from geostationary orbit the images will be highly skewed, one day something akin to a pole sitting satellite (see ESA) may be used to provide coverage.