NASA considers sending a telescope to outer solar system

Dec 20, 2011 By Bruce Dorminey, Universe Today
ZEBRA (Zodiacal dust, Extragalactic Background and Reionization Apparatus) is a small, passively cooled optical to near-infrared instrument package that could be added to an outer solar system probe. Credit: NASA/JPL/Caltech

Light pollution in our inner solar system, from both the nearby glow of the Sun and the hazy zodiacal glow from dust ground up in the asteroid belt, has long stymied cosmologists looking for a clearer take on the early Universe.

But a team at NASA, JPL and Caltech has been looking into the possibility of hitching an to a survey on a mission to the .

Escaping our Inner Solar System’s Polluted Purple Haze

The idea is to use the optical telescope in cruise phase to get a better handle on extragalactic background light; that is, the combined optical background light from all sources in the Universe. They envision the telescope’s usefulness to kick in around 5 Astronomical Units (AU), about the distance of Jupiter’s orbit. The team then wants to correlate their data with ground-based observations.

One goal is to shed light on the ’s epoch of reionization. Reionization refers to the time when ultraviolet (UV) radiation from the universe’s first stars ionized the intergalactic medium (IGM) by stripping electrons from the IGM’s gaseous atoms or molecules. This period of reionization is thought to have taken place no later than 450 million years after the Big Bang.

ZEBRA, the Zodiacal dust, Extragalactic Background and Reionization Apparatus, is a NASA JPL concept that calls for a $40 million dollar telescope comprised of three optical/near-infrared instruments; consisting of a 3 cm wide-field mapper and a 15 cm high-resolution imager. However, NASA has yet to select the ZEBRA proposal for one of its missions.

But to learn more, we spoke with the ZEBRA Concept lead and instrument cosmologist Jamie Bock and astronomer Charles Beichman, both of NASA JPL and Caltech.

Dorminey: What is zodiacal light?

Beichman: It’s a bright source of diffuse light in our own solar system from dust grains that emit because they have been heated by the and are radiating by themselves

or reflect sunlight. If you go out on a very clear dark moonless light, you can see the band of this light from this dust. It follows the plane of the ecliptic. That dust mostly originates from material in the that gets ground up into little particles after some big collision.

Dorminey: What would getting past this zodiacal dust mean for observations?

Beichman: Imagine sitting in the Los Angeles basin and you’ve got all this smog and haze and you want to measure how clear the air is out at Palm Springs. You have to be able to subtract off all the haze between here and there and there’s just no way to do it with any accuracy. You have to drive out of the basin to get out of the smog.

Dorminey: How would this help in studying this extragalactic background?

Bock: The Extragalactic Background Light (EBL) measures the total energy density of light coming from outside our galaxy. This light gives the sum of the energy produced by stars and galaxies, and any other sources, over the history of cosmic time. The total background can be used to check if we correctly understand the formation history of galaxies. We expect a component of the background light from the first stars to have a distinct spectrum that peaks in the near-infrared; this can tell us how bright and how long the epoch was when the first stars were forming. Unfortunately, zodiacal light is much brighter than this background. But by going to the orbit of Jupiter, the zodiacal light is 30 times fainter than at Earth, and at the orbit of Saturn it is 100 times fainter.

In our solar system, anybody observing the skies on a moonless night far from city lights can see the sunlight that is scattered by dust in our asteroid belt. Called zodiacal light and sometimes the "false dawn," this light appears in this artist's concept as a dim band stretching up from the horizon when the Sun is about to rise or set. The light is faint enough that the disk of our Milky Way galaxy remains the most prominent feature in the sky. (The Milky Way disk is shown perpendicular to the zodiacal light). Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Dorminey: Would you have to hitchhike on a NASA mission or could it be a partnership with another space agency, like ESA for instance?

Bock: We have been exploring the cheapest incremental cost approach, partnering with a planetary mission. But we could partner with another space agency. The European Jupiter Icy Moons Explorer (formerly JGO) is now competing for the next L-class mission launch in the early 2020’s and is an attractive possibility for a contributed cruise-phase science instrument. Each approach comes with a different cost and partnership environment.

Dorminey: Is the prime driver for the EBL telescope to get beyond the zodiacal dust or does 5 AU also offer an observational advantage in terms of achieving faintness of magnitude?

Bock: There is an observing advantage due to the [darker solar system] background. With such a small telescope, we are not trying to exploit this benefit but future observatories could. We will measure the zodiacal brightness to Jupiter and beyond, and this may motivate astronomical observations with telescopes in the outer solar system in the future.

Dorminey: What sort of data downlink challenges would you encounter?

Bock: The data requirements are perhaps smaller than one might first expect, because our images are obtained with long [observational] integrations at moderate spatial resolution. For the planetary proposal we studied in detail, the total data volume was 230 gigabytes, with about 65 percent of this data being returned from Jupiter and out to Saturn. The telescope pointings operate autonomously.

Dorminey: What about radiation from Jupiter interfering with the optics and CCD cameras on the telescope?

Beichman: What you’d do is stop making the EBL observations while close to Jupiter. The radiation problems are significant, so you would only do observations before and after passing Jupiter.

Dorminey: What would your instruments do that NASA’s planned James Webb Space Telescope (JWST) wouldn’t?

Bock: JWST will likely detect the brightest first galaxies, and depending exactly how galaxies formed, will miss most of the total radiation due to the contribution of many faint galaxies. Measuring the extragalactic background gives the total radiation from all the galaxies and provides the total energy. Furthermore, we don’t need a large telescope; 15 cm is sufficient.

Dorminey: What about planetary science with the telescope?

Bock: Our instrument specializes in making low surface-brightness measurements. We made specific design choices to map the zodiacal dust cloud from the inner to the outer . A 3-Dimensional view will let us trace the origins of interstellar dust to comets and asteroid collisions. We know there are Kuiper-belt objects beyond the orbit of Neptune, and it is likely there is dust associated with them as well.

Dorminey: How long would this telescope function?

Bock: After the prime observations complete, it would certainly be possible that the original team or an outside party could propose to operate the telescope. One exciting science case is parallax micro-lensing observations; observations that use the parallax between Earth and Saturn to study the influence of exo-planets orbiting the stars producing a micro-lensing event. Other science opportunities include maps of the Kuiper Belt in the near-infrared; stellar occultations by Kuiper Belt Objects; and mapping more EBL fields for comparison with other surveys.

Dorminey: How would the telescope’s initial observations potentially shake up theoretical cosmology?

Beichman: Whenever you do a measurement that’s a factor of a hundred times better than before, you always get a surprise.

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User comments : 30

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Nanobanano
1.6 / 5 (8) Dec 20, 2011
The radiation problems are significant, so you would only do observations before and after passing Jupiter.


This makes no sense. It's as if they believe every probe headed to the outer solary system "must" have a close encounter with each planet. I mean, Jupiter could well be on the opposite side of the SS from where the probe is actually going at the time of closest approach, After all, it's 5 a.u. from the Sun. The orbit sweeps an elipse that is like 16 a.u. around.

Unless they put this on a mission that is actually aiming for Jupiter it makes no sense to even worry about this, and then again, why would any numbskull put this instrument on a probed aimed for Jupiter if it's a potential problem for the instrument?

Just bad question and bad response.
Nanobanano
2.4 / 5 (5) Dec 20, 2011
observations that use the parallax between Earth and Saturn to study the influence of exo-planets orbiting the stars producing a micro-lensing event.


First thing's first.

Use the parallax to nail down the real distance to certain key "unknown distance" objects, such as Betelgeuse, which has relevance to actually determing the REAL mass and luminosity of all stars, instead of the bs "off by plus 100% or minus 50%" BS measurements they have now...

They're talking about using it for microlensing, and they can't even tell exactly how far, or how big the stars are to begin with.

So first principles first.

Nail down the distance and mass of the stars to a relevant margin of error, then you can worry about microlensing later. You know, 1% margin of error in distance and mass, instead of 50% to 100%. At least get that good, before you worry about an alleged planet that has a mass a million times less...
Sonhouse
5 / 5 (11) Dec 20, 2011
The radiation problems are significant, so you would only do observations before and after passing Jupiter.


This makes no sense. It's as if they believe every probe headed to the outer solary system "must" have a close encounter with each planet. I mean, Jupiter could well be on the opposite side of the SS from where the probe is actually going at the time of closest approach, After all, it's 5 a.u. from the Sun. The orbit sweeps an elipse that is like 16 a.u. around.

Unless they put this on a mission that is actually aiming for Jupiter it makes no sense to even worry about this, and then again, why would any numbskull put this instrument on a probed aimed for Jupiter if it's a potential problem for the instrument?

Just bad question and bad response.


NASA would plan to use Jupiter as a sling to accelerate it further out towards Saturn. That's why they talk about Jupiter in the first place, free acceleration. They didn't mention that in the article.
Nanobanano
1 / 5 (7) Dec 20, 2011
NASA would plan to use Jupiter as a sling to accelerate it further out towards Saturn. That's why they talk about Jupiter in the first place, free acceleration. They didn't mention that in the article


1, I'm aware of the sling shot method of accelerating probes.

2, Better "free" propulsion methods with higher max velocities now exist, including the ESA's electric solar sail design.
Dokudango
4.4 / 5 (5) Dec 20, 2011
QC, you should go work for NASA; you are such a smart guy.
Nanobanano
1.7 / 5 (12) Dec 20, 2011
QC, you should go work for NASA; you are such a smart guy.


Maybe I should.

The existing paradigm has done absolutely nothing useful in my entire life. They haven't "really" even made any progress in manned space flight at all in my life, and the probes are all over budget, under-built things that either fail, or just don't have any potential whatsoever to do any useful science.

"Ooh, pretty picture, big deal, *yawns*, everybody forgets/doesn't care, nothing else ever comes of it." - Past 30 years of NASA.
Pirouette
1.9 / 5 (9) Dec 20, 2011
@Nano
Since Voyager #1 & #2 are still going strong since the 1970s and #1 is almost to the point where the influences of the Sun are nil, heading out beyond the Solar System and into intersolar space, I think that the new telescope could be loaded aboard a new probe manufactured with Voyagers' technology (a whole lot cheaper back then) and sent out to intersolar space also. I say intersolar to mean the space between the stars, but "intrasolar" might be more apt?
Anyway, the telescope will be very costly, but the Voyager type probe, if NASA or ESA uses the tried and true blueprints, software, hardware of the Voyager projects and whatever other instruments are desired, the resulting cost should be much less than creating a whole new design to carry the telescope to its destination between the stars. The designs exist already, unless they were destroyed or lost like the Moon rocks. :(
What is your opinion on this?
Pirouette
2 / 5 (8) Dec 20, 2011
ooops. . .I should have said "interstellar space". My bad. :(
It may take 30 plus years to see actual results from the telescope aboard a Voyager type spacecraft. That's the only drawback, unless a faster means of propulsion can be included, which means more costs.
FrankHerbert
1 / 5 (54) Dec 20, 2011
I'm pretty sure the Hubble is more capable than anything we could have strapped to a Voyager-style spacecraft in the 1970's, even taking into account the diminished influence of the Sun.

It stands to reason that anything we would put on an interstellar spacecraft today would be overshadowed by something we could fling into orbit by the time the interstellar spacecraft reaches its optimum distance from Earth.
Vendicar_Decarian
3 / 5 (4) Dec 20, 2011
I would prefer a Lagrange interferometer so that the atmospheres of some of the planets found so far could be chemically analyzed.

Pirouette
3 / 5 (4) Dec 20, 2011
They haven't found a planet yet that is comparable to Earth in every way and that's just the right distance from its star.
Vendi. .would your interferometer look something like this?
http://www.asc.rs..._eng.htm

The new telescope MIGHT fit onto a Voyager type spacecraft if they could make the spacecraft a bit bigger and ramped up its propulsion system to travel at a greater speed into interstellar space.
Pirouette
2.3 / 5 (3) Dec 20, 2011
A lot of us may not be around in the next 30 years, but given the successes of Voyagers 1 & 2, if it's a lot cheaper to build and deploy, then maybe a lot of money will be saved.
that_guy
5 / 5 (1) Dec 20, 2011
I never knew that the asteroid dust created that light. I always wondered about it. Sometimes i thought it was from a city over the horizon or pollution/dust in the air. (Even when the air is clear and there are no cities nearby.

Other notes to the comments here...

Hubble is considerably bigger than voyager. That said, large rockets are comparably cheaper to our economy than they were in the 50s and 60s.

@nano - Improved parallax measurements with a telescope like this would only improve moderately at best. You would really need something with (very)high resolution and low variability to get significant gains. If you had a second telescope (Also outside the asteroid belt) paired with this one, then you could really crank it up.
Pirouette
2.3 / 5 (3) Dec 20, 2011
The way I read the article, they're saying that the distance to the new EBL telescope's destination past all the planets in the outer SS would be the EQUIVALENT of Jupiter's orbit going around the Sun, meaning the distance from point A, back around to point A again. If you take the distance of Jupiter's orbit and stretch it out into a line rather than an ellipse, that would be the distance, in a more or less straight line, past Jupiter that the telescope plus probe would have to travel to get to interstellar space. . .but somewhere along that imaginary "straight" line is where the telescope will begin to operate (at around 5 AU).
NMvoiceofreason
3.7 / 5 (6) Dec 21, 2011
The planned mission would deliver wonderful science. Better data could be obtained, for less cost (and time) by sending the probe directly to the Sun, for a gravity assist straight "up" (perpendicular) out of the plane of the Solar System.

Would also get us some perspective we never get to see. Two additional missions with RF telescopes, one "down", one "up", could give us a VLBI of 10 AU.

Cheap at twice the price.
Cynical1
3 / 5 (2) Dec 21, 2011
Excellent reasoning, NM. I actually like that concept better than getting out past Jupiter.
Blakut
5 / 5 (1) Dec 21, 2011
44cm... rather small for a telescope, no?

And gravity assist only boosts your speed relative to the system you are in, you get no "free" acceleration no more that you would get "free energy" out of something. Using the Sun for example you would get a boost relative to the motion of the sun through the galactic plane. Gravity assist "straight up" doesn't make much sense.
antialias_physorg
4 / 5 (4) Dec 21, 2011
1) Nowhere in the orbit does it say that this telescope has to go anywhere near the vicinity of Jupiter

2) If Jupiter is used as a slingshot then that's not a problem - since the time it spends close to Jupiter will be rather small (so the time it is not able to get peak resolution will be minimal - and we'll probably want to have it pointed AT Jupiter for the duration of the flyby, anyways)

3) If we slingshot it we should slinghot it around Mars or Venus at the latest heading at right angles out of the plane of the solar system (as most dust is in the plane). Probably much better to slingshot it around the Moon, back to Earth and then straight up/down

4) Slingshot around the sun is probably too dangerous, as the radiation is much more intense and over a vastly longer time - leading to much added risk for the electronics and detectors on board.
Pirouette
2.3 / 5 (3) Dec 21, 2011
Aiming it toward the Sun for a slingshot effect IS too dangerous. It would be far better to aim it more or less in a straight line (with adjustments) toward Jupiter, slingshot it past Jupiter and out of the Solar System.
The inner casing that houses the telescope is 44 cm x 44 cm x 20 cm, which seems pretty small, even with the outer casing. The whole package should fit very nicely atop a space probe such as Voyager or New Horizons. Building another Voyager would be cheaper than planning, designing and executing a whole new probe just for the telescope and its other instruments would be a waste of taxpayers' money and the time involved. They have the blueprints, et al, for Voyager and New Horizons. Why not utilize them? If something bad had happened to the Voyagers and they were lost somehow, ir would be worth trying out a new probe, but both Voyagers are alive and well, so the evidence shows that the design and engineering is space-worthy.
NotAsleep
5 / 5 (2) Dec 21, 2011
44cm... rather small for a telescope, no?

Just giving it the measurement of "44cm" is a bit misleading. There's a lot of other info required to determine the telescope's effectiveness. It's like going out and buying a "100X" telescope instead of a "50X" telescope. The "X" factor provides limited information by itself, you need to know focal length, mirror/lense diameter, telescope type, etc.

Also, 44cm may be small for ground-based telescopes that have to see through the atmosphere but are likely more than sufficient in space, especially if placed in the outter solar system. While bigger is better, in the game of cost vs. benefits, this is probably the best telescope they can send for the cost
Pirouette
3 / 5 (2) Dec 22, 2011
Those dimensions are in the illustration with the article. If small is just as efficient as a bigger telescope, so much the better. That's less weight for the rocket boosters and the probe's own thrusters. JPL will probably steer it toward Jupiter, then shoot it out of the SS. The only drawback is the time involved for it to reach interstellar space. As I've said before, a lot of us may not be around when the probe reaches 5 AU.
NotAsleep
5 / 5 (1) Dec 22, 2011
Well, no... they don't unless you found a picture with more information on it. The picture above seems to give the physical dimensions of the device, which still isn't particularly helpful.

I'd like comments from someone that is familiar with what TYPE of telescope this is. I'm assuming it isn't optical
that_guy
3 / 5 (2) Dec 22, 2011
I'd point out that the increase in detail or light collecting ability is rather small compared to some other challenges posed by making the satellite so small. (Vs putting a bigger telescope near earth.)

The maximum theoretical light collecting ability is based on apeture size. That is 44cm in this case, vs 240cm for hubble. Even if hubble is significantly hampered by the dust, it would be hard for this telescope to significantly improve on that.

For this telescope to significantly exceed hubble, it needs to have a mirror precision at an order of magnitude better than hubble (A smoothness variation of less than 10 nm to beat the corrected hubble), it will also bump up against physical limits clarity because of light wavelength to the sensor size (specifically the size of the pixel element in the CCD.)

I mean, honestly, they just need to go big or go home. This is an expensive mission to begin with, they shouldn't half ass it.
Pirouette
3 / 5 (2) Dec 23, 2011
I'm sure that NASA will take everything into consideration and make improvements in quality and efficiency over that of the Hubble telescope. As to the cost of such a project and all that's involved. . .NASA is famous for going over budget and repeating past experiments but with newer technology. This new telescope will have the advantage of being OUT of the range of the hazy light and dust of our SS, and in the darkness of interstellar space, will send back perfect high resolution images to Earth with its wide-field camera and specroscope. The only drawback is that other galaxies and star systems have their own haze and dust, but the specroscopy should take care of that. They should also include a gamma and xray detector that will measure radiations in outer space that are passing through the instruments. If mankind does go out to other stars eventually, that information will be of enormous importance.
antialias_physorg
3.7 / 5 (3) Dec 23, 2011
The maximum theoretical light collecting ability is based on apeture size. That is 44cm in this case, vs 240cm for hubble.

Apples and oranges.
Hubble is designed to look at stars/galaxies/nebulae.
ZEBRA is designed to look at the background. It doesn't need the resolution of Hubble it just needs a higher sensitivity.

The two (and the JWST) complement each other so that one can gather data that is then used to refine the pictures of the others.
that_guy
3 / 5 (2) Dec 23, 2011
Apples and oranges.
Hubble is designed to look at stars/galaxies/nebulae.
ZEBRA is designed to look at the background. It doesn't need the resolution of Hubble it just needs a higher sensitivity.

The two (and the JWST) complement each other so that one can gather data that is then used to refine the pictures of the others.

That's even questionable. Hubble has six times the light collecting capability and the advantage of a larger apeture when focusing the light.

This may be able to capture slightly more accurate contrast or slightly more accurate spectroposy without the dust, but the limitations of the size difference make any advantages hard to gain especially in light of the magnified cost.

And if they screw up, they can't go back and fix it. (Had to go there)

Honestly, if they want to try something like this, they should fit it on an existing probe with other missions - like new horizons - and do this experiment while the probe is in transit.
antialias_physorg
3.7 / 5 (3) Dec 23, 2011
Hubble has six times the light collecting capability

But it gets a lot of noise at low (infrared) energies from dust.
Nanobanano
1 / 5 (1) Dec 25, 2011
If you had a second telescope (Also outside the asteroid belt) paired with this one, then you could really crank it up.


That was the idea I've been hoping someone at NASA or ESA would implement.

I called for 2 telescopes orbiting along each basic plane, offset by half of an orbit. I'd propose somewhere out past Jupiter if possible. So the orbits would be on each plane:

XY 2
XZ 2
YZ 2

The 2 telescopes on each plane would be offset by a half orbit, and you'd use a few additional (existing?) satellites as relays to synchronize their time to get very precise 2-point, 3-point, and even 4, 5, and 6 point perspective, parallax measurements of important stars.

Synchronized measurements from opposite sides or the orbit is much more useful than sequential measurements offset by half-orbit in time...

Additionally, once the Parallax measurements are determined for the most important stars, you can then us this to produce a more accurate star map in 3 dimensions.
that_guy
not rated yet Dec 27, 2011
Hubble has six times the light collecting capability

But it gets a lot of noise at low (infrared) energies from dust.

That's a fairly narrow advantage. Why I think that there's some advantage to be gained, but if they loaded it on something meant to go out that way anyways, it would make it more cost effective and reasonable.

Who said that probes shouldn't hitchhike?
antialias_physorg
not rated yet Dec 27, 2011
Who said that probes shouldn't hitchhike?

The guys doing the fuel calculations.

Hubble is BIG.

Look - these guys are astrophysicists. They know that Hubble exists. Give them enough credit that they have switched on a couple of brain cells before proposing this in the format that they did.
Space missions enter a pretty fierce competition. Only a small fraction of proposed programs actually get realized. Think they would have proposed this setup if they didn't think it had at least a small chance of passing muster?

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