Missions | Centauri Dreams

Science at the Edge of the Solar System

by Paul Gilster | May 30, 2006 | Interstellar Medium, Missions | 1 Comment

The Interstellar Boundary Explorer is clearly a mission whose time has come. Scheduled for launch in 2008 and recently confirmed for mission implementation, IBEX will provide global maps of the distant interactions where the heliosphere (the 'bubble' of space carved out by the solar wind) meets the interstellar medium. All of this at a time when Voyager 1 is thought in some quarters to have already crossed the 'termination shock,' that region where the solar wind is slowed as it encounters interstellar gases; some evidence suggests that the spacecraft then moved back into the supersonic solar wind. Image: The Sun's movement through the local interstellar medium. IBEX should tell us much about the boundary separating the heliosphere from this region. Credit: Southwest Research Institute. The Voyager findings remain controversial thanks to magnetic field and cosmic ray measurements that suggest different interpretations, but it's clear that Voyager is at the very edge of the...

Gravitational Lensing Writ Large

by Paul Gilster | May 25, 2006 | Deep Sky Astronomy & Telescopes, Missions | 2 Comments

Here's gravitational lensing with an exclamation point. A single quasar is shown in the Hubble photograph below as five star-like points. Gravitational lensing occurs when the gravitational field of a massive object bends and amplifies the light from a much further object behind it. And although we've had numerous examples of such lensing, this is the first time the intervening object was an entire galactic cluster. Image: Five star-like images are actually a single distant quasar. Credit: ESA, NASA, K. Sharon (Tel Aviv University) and E. Ofek (Caltech). The cluster in question is SDSS J1004+4112, some seven billion light years away; the quaser is roughly ten billion light years distant. It took spectral data from the Keck I 10-meter telescope to demonstrate that these images were all of the same quasar. The quasar itself is the core of a galaxy, with a black hole at its center creating its intense light by interactions with nearby gas and dust. Note too in this picture the images of...

A Boost for Innovative Interstellar Explorer

by Paul Gilster | Apr 22, 2006 | Advanced Rocketry, Missions | 9 Comments

The Innovative Interstellar Explorer mission discussed recently in these pages has received new support in a study of alternative propulsion concepts. IIE, you may remember, would use radioisotope electric propulsion (REP), tapping xenon as propellant. The mission's goal is to deliver a scientific payload to 150-200 AU within a 15 to 20 year time frame; the concept thus tracks earlier mission concepts built around solar sails and allows useful comparisons beween the various propulsion methods that have been proposed for such deep space work. In a paper to be published as a chapter in a book on NASA 'Vision' missions this summer, Thomas Zurbuchen (University of Michigan) and a team of researchers discuss the specifics of powering such a probe by nuclear methods and find them wanting. The paper is so rich that I want to discuss several issues from it in coming weeks. For now, though, let's consider the propulsion dilemma as seen by scientists running the numbers using existing...

On Interstellar Dust and Fast Probes

by Paul Gilster | Apr 10, 2006 | Interstellar Medium, Missions | 1 Comment

Here's why we'll have to know a great deal about the interstellar medium -- the stuff between the stars -- before we ever send out probes at a substantial fraction of lightspeed. The gas and dust forming into dark, concentrated knots in the image below creates so-called 'Bok globules,' named after astronomer Bart Bok, who hypothesized their existence back in the 1940s. They're hundreds of light years in size and, when perturbed, can form concentrated pockets of gas and dust that have the potential of turning into stars. But not all of them do become stars. In the image, we're looking at NGC 281, a nearby nebula and star-forming region some 9,500 light years away from Earth in the direction of Cassiopeia. In this region, many of the dust knots seem to be dissipating before stellar formation actually occurs. You can also see the bright blue stars of a cluster called IC 1590, whose young and massive stars put out enough solar wind to energize the surrounding hydrogen gas of the nebula...

A Practical Mission to the Interstellar Medium

by Paul Gilster | Apr 3, 2006 | Interstellar Medium, Missions | 7 Comments

The first true interstellar mission may be on the drawing board right now. Yes, Voyager 1 has already crossed the termination shock 94 AU out and is still returning data, but we've never had a mission targeted from day one at interstellar space. Yet that region just beyond the influence of the Sun -- the Very Local Interstellar Medium -- is crucial; it will tell us much about the interface between the solar wind and deep space. Probing it will create new data on everything from gravitational waves to anomalous forces like those that may be acting on the Pioneer spacecraft, not to mention setting the stage for future missions. Now dubbed the Innovative Interstellar Explorer, the concept is for a robotic mission beyond the heliopause, and as refined through studies led by Ralph McNutt (Johns Hopkins University Applied Physics Lab) for NASA's Institute for Advanced Concepts, and now through continuing development as a NASA mission study, the IIE would take a 1000-kg payload on the first...

Short Takes for the Weekend

by Paul Gilster | Apr 1, 2006 | Astrobiology and SETI, Exoplanetary Science, Missions, Outer Solar System | 1 Comment

In which the hapless author tries to clear out his growing backlog of material. This may have to become a regular feature, since the amount of new information coming in about the extrasolar planet hunt alone would be enough to keep Centauri Dreams busy all day, not to mention continuing work on propulsion concepts from solar and magnetic sails to antimatter and ongoing discoveries relating to dark matter and energy. Herewith, then, a few shorter items compressed only for reasons of space and time, so to speak. On Transit Windows and Red Dwarfs The planet around GL 581, an M-class red dwarf discovered last September, is unusually interesting because of its low mass, roughly 17 times that of Earth. This is probably a Neptune-class world with some possibility of being observable through transits -- i.e., its orbit may cross its primary as seen from Earth, making it a candidate for the transitsearch.org collaboration. But the last transit window on March 28 was rendered useless by cloud...

Henry Hsieh on Main-Belt Comets

by Paul Gilster | Mar 29, 2006 | Missions, Outer Solar System | 3 Comments

Centauri Dreams recently discussed the discovery of so-called 'main-belt comets' -- icy objects found in asteroid-like orbits that apparently formed in the inner Solar System rather than on its outer edges. The work, performed by Henry Hsieh and David Jewitt (University of Hawaii) raises questions about the origins of Earth's water supply, which had been thought to have been delivered by cometary impacts on the primordial Earth. Could this water have, in fact, been delivered by main-belt comets, and could a mission to one of them yield the answer? A sharp-eyed reader wanted to know more: assuming we flew such a mission, how could we pin down the main-belt comets as the source, as opposed to the huge population of long-period comets with their highly elliptical orbits? Henry Hsieh was kind enough to respond: In recent years, the debate over the origin of the Earth's water has focused on the so-called D/H (deuterium to hydrogen) ratio of ocean water, comet water, and meteorite water...

Nothing Yet from Pioneer 10

by Paul Gilster | Mar 6, 2006 | Missions | 3 Comments

As reported by Larry Kellogg, the recent attempt to pick up a signal from Pioneer 10 may have come up short, although the team working on the project is processing the data in the attempt to pin down anything that isn't noise. Says Kellogg: Distance makes a difference... The 8 watt transmitter wouldn't be putting out a full 8 watts (a night light of power) and the signals seen at Earth were buried down in the noise you get from just pointing an antenna out into space. It is like looking for a needle in the front lawn down in the grass. One spike looks a lot like the one next to it. If you see something you think is your needle you can narrow the band pass filter and magnify what you are looking at. You don't see anything next to it though and so you have to look back and fourth and hope you recognize your needle. We haven't had any signals from Pioneer since 23 January 2003; the last telemetry data were received on 27 April 2002. With no real-time detection of the spacecraft's...

Listening for Whispers from Pioneer 10

by Paul Gilster | Mar 2, 2006 | Missions | 0 Comments

The attempt to contact Pioneer 10, clearly for the last time, is on for March 3, 4 and 5. That according to Larry Kellogg on his To the Moon, Mars and Beyond weblog, which bears quoting this afternoon: Earth has come around the Sun and will be directly within Pioneer 10's antenna pattern, if an antenna pattern there might be. Might be, because the fixed frequency oscillator is dead and the only way to wake up the spacecraft is to send up a strong signal which will wake up the variable frequency oscillator and let the spacecraft send back a signal at a known offset from what it sees coming up. This will be the last time Earth will be here as the Sun drags us along as it goes on its way around the Solar System. Each year Earth moves over just a bit in space and in the past you could command Pioneer 10 to re-align itself to look at a 400 KW up-link signal from Earth but there is not enough power on board Pioneer 10 to do that now and no one is sending commands anyway. [Mission long over...

A News Conference and a Launch

by Paul Gilster | Jan 19, 2006 | Missions | 0 Comments

This is shaping up to be a busy day, starting with good news from the Stardust mission. Having opened the sample return capsule at Johnson Space Center in Houston, the science team found that the sample tray held numerous particles captured not only from comet Wild 2 but interstellar particles collected during the missions' seven year journey. Stardust principal investigator Donald Brownlee said it all: "The collection of cometary particles has exceeded our expectations. We were absolutely thrilled to see thousands of impacts on the aerogel." Coming up at 1100 EST (1600 GMT) is a news conference held by Stardust team members in Houston, with coverage on NASA TV (and I notice that NASA will offer video of the opening of the Stardust cannister at 1500 EST today). Also imminent is another attempt to launch New Horizons, now scheduled for 1308 EST (1808 GMT), and available both through NASA TV and useful pages like the ELV Countdown Portal at Kennedy Space Center. The New Horizons launch...

A Wish for New Horizons

by Paul Gilster | Jan 18, 2006 | Culture and Society, Missions | 2 Comments

Yesterday's brief and unplanned exercise in 'liveblogging' was caused by an odd discovery: the only way for this observer to track the New Horizons launch was through the Internet. With over 200 channels available through cable television, I found that channel surfing through all of them yielded not one with live NASA coverage. Now ponder this. Centauri Dreams is based near North Carolina's Research Triangle Park, with three major universities within easy driving distance. The woods are full of PhDs, the area priding itself on high tech. With all these resources, there was not a single cable channel that could be devoted to the first mission to Pluto/Charon ever launched. You can imagine what kind of fare was available on many of the channels that were available. Around the same time, I also noted the slowdown in NASA servers as the launch progressed and received e-mails from people who were having trouble accessing NASA TV. Thus the attempt to post updates on the launch holds...

New Horizons Launch Aborted

by Paul Gilster | Jan 17, 2006 | Missions, Outer Solar System | 0 Comments

Centauri Dreams is not conceived as a streaming news site, but the NASA servers are slammed, so I'll update as needed until we get New Horizons off the ground. Update times are GMT (subtract 5 for EST). Update: 2022 Launch abort, with at least a 24-hour turnaround. Launch now scheduled for tomorrow at 1816 GMT (1316 EST). 2019: Countdown resumes at T-4 minutes. 2001: Launch now re-scheduled for 2023 GMT (1523 EST). We're nearing the outer edge of today's launch envelope. Ground-level winds are now problematic. 1950: Upper level winds remain a concern although launch is still set for 2005 GMT (1505 EST). No technical issues with the Atlas V; the problem is solely meteorological at this point. 1946: Launch time now set for 2005 GMT (1505 EST), due to a problem with the Deep Space Network that has now been resolved. An earlier delay had been caused by upper level winds. ----------- All eyes are on Launch Complex 41 this morning, and on the clock. The New Horizons launch is scheduled for...

Of Missions and Deep Time

by Paul Gilster | Jan 16, 2006 | Culture and Society, Missions | 2 Comments

The successful return of the Stardust samples offers a chance to study cometary materials up close, surely deepening our understanding of the origins of the Solar System. But it also serves as a reminder of the time frames in which deep space missions must be flown. At that, Stardust has been a relatively swift mission, traveling some 2.88 billion miles in a seven-year journey. But ten years of planning also went into that journey, and design work goes back over 20 years. Thus Don Brownlee's comment on the mission's origin. "I have been waiting for this day since the early 1980s when Deputy Principal Investigator Dr. Peter Tsou of JPL and I designed a mission to collect comet dust," said Dr. Brownlee. "To see the capsule safely back on its home planet is a thrilling accomplishment." As well it must be, for Brownlee (University of Washington, Seattle) is principal investigator for the entire Stardust mission. Now thoughts turn to New Horizons, just over a day from launch. Scheduled to...

Solar Sail to the Heliopause

by Paul Gilster | Dec 2, 2005 | Missions, Sail Concepts | 0 Comments

Proposals for realistic interstellar missions are not a new thing; in fact, several concepts grew out of work in the early 1980's at the Jet Propulsion Laboratory, starting with the 'Thousand Astronomical Units' (TAU) mission, and extending to recent studies on the mission commonly referred to as the Interstellar Probe. By 'interstellar,' I mean journeys not to a nearby star but (a much needed first step) a journey to the interstellar medium beyond the heliosphere, that region carved out by the influence of the Sun's solar wind. We have one vehicle there now, as Voyager 1 seems to be crossing the heliopause into true interstellar space. What we need to ponder next is how to build a spacecraft specifically designed for heliopause studies. A team of European researchers is now tackling the job. Designed as part of the European Space Agency's excellent Technology Reference Studies, the Interstellar Heliopause Probe is put forth as a mission to reach 200 AU within 25 years, using a...

Nuclear Pulse Propulsion Re-Examined

by Paul Gilster | Nov 24, 2005 | Breakthrough Propulsion, Missions | 11 Comments

Consider two hypothetical spacecraft. The Orion vehicle would have worked by setting off low-yield nuclear devices behind a massive pusher plate, driving forward a payload attached at a safe distance from the pusher (and protected by mind-boggling shock absorbers). Even if we had the nuclear devices at our disposal, agreed to use them for such a purpose, and found the political will to construct an Orion craft for deep space exploration, a problem still remains: most of the energy from the nuclear blasts is dissipated into space, and the craft thus requires a huge critical mass of fission explosives. Orion, in short, is not efficient in using its energies. Now consider Project Daedalus, the hypothetical mission to Barnard's Star designed by members of the British Interplanetary Society back in the 1970s. Daedalus was designed to use fusion microexplosions instead of fission. One of the reasons the Daedalus craft demanded as much fuel as it did is that the ignition apparatus, whether...

Hayabusa in the Shadows

by Paul Gilster | Nov 21, 2005 | Advanced Rocketry, Missions | 2 Comments

The Japanese Hayabusa spacecraft has always seemed to have a couple of strikes against it, at least in terms of media coverage. Never much in the spotlight, the ambitious attempt to explore and bring back samples from the asteroid Itokawa has been all but eclipsed by China's recent manned orbital ventures. And Centauri Dreams suspects that's a primary problem: robotic missions don't draw the public eye the way risky manned flights do, even if the scientific payback from the former is often immeasurably greater. Now Hayabusa is encountering a different set of problems. The Minerva robot was to have landed on Itokawa last week, but disappeared after its release. A lower profile issue has been solar flare damage to the spacecraft's solar panels and continuing problems with its positioning control system. And now we have word of a mission-endangering glitch: Hayabusa failed to touch down on the tiny asteroid when the attempt was made on Sunday. "I don't think it landed," project leader...

FOCAL: Using the Gravitational Lens

by Paul Gilster | Nov 16, 2005 | Missions, Sail Concepts | 0 Comments

Among the curious features of a gravitational lens is the way it focuses electromagnetic waves. Supposing we could build a spacecraft like Claudio Maccone's FOCAL concept, a vehicle designed to reach the Sun's gravity focus at 550 AU. From that vantage, the electromagnetic radiation from an object occulted by the Sun (i.e., on the other side of the Sun from the spacecraft), would be amplified by a factor of 108. Such amplification could be exceedingly useful for astronomy at all wavelengths, and even for SETI. But note this key difference between a gravity focus and its optical counterpart: in an optical lens, the light diverges after the focus. Light focused by the Sun's gravitational lens, however, stays fixed along the focal axis as you move to distances greater than 550 AU. Quoting Maccone: "It is true that one does not have to stop FOCAL at just 550 AU, because every point along the straight line trajectory beyond 550 AU still is a focal point." It was in the 1980s that Alenia...

On Deflecting Near Earth Objects

by Paul Gilster | Oct 31, 2005 | Asteroid and Comet Deflection, Missions, Outer Solar System | 0 Comments

The B612 Foundation continues to examine the danger of near-Earth objects (NEOs). As noted earlier in these pages, B612 points to the continuing evidence for asteroid and comet impacts and their role in shaping the planet's history; the much discussed demise of the dinosaurs, due to a likely asteroid strike in the Yucatan, is but one of the instances where the planetary ecology has been altered. We know that the Earth orbits in a swarm of near-Earth asteroids, with a probability of collision in this century that the Foundation pegs at an unacceptably high 2 percent. Given these concerns, and the possible dangers posed by the object called NEO 99942 Apophis, the Foundation has engaged in a dialogue with NASA about possible missions to this asteroid. Apophis (also known as 2004 MN4) is on course for a near-miss in 2029 , with the 400-meter asteroid approaching to within 32,000 kilometers. What happens afterwards as the near-miss itself disrupts the orbit of this object remains a...

A Gravitational Lens at Work

by Paul Gilster | Oct 27, 2005 | Deep Sky Astronomy & Telescopes, Missions | 0 Comments

Gravitational lenses of the sort discussed in yesterday's post are now widely discussed. The idea that gravity can bend light may seem counterintuitive but we've seen numerous demonstrations of the effect, starting with the famous eclipse studied by Arthur Eddington in 1919. Hoping to test Einstein's general theory of relativity, Eddington traveled to the island of Principe, off the coast of West Africa. There, despite initially cloudy skies, he was able to take the crucial photograph that verified Einstein. Stars in the Hyades Cluster that should have been blocked by the Sun were revealed in the image, offset by an amount close to that predicted by Einstein. Some have questioned whether Eddington's equipment was sufficiently precise to make accurate readings, but whatever the case, the bending of light as a result of gravity has stood up. Among the various images that show this effect in deep space, none is as dramatic as the one below. Here we're looking at multiple bluish images...

A Mission to the Gravity Focus

by Paul Gilster | Oct 26, 2005 | Astrobiology and SETI, Missions | 1 Comment

Voyager 1 is, in a sense, our first interstellar spacecraft, with evidence mounting that it has reached the heliopause, that area marking the boundary between the Sun's outward-flowing particles and the true interstellar medium. The New Horizons mission, scheduled for launch in January, will go on to explore at least part of the Kuiper Belt. But what will our first true interstellar mission be; i.e., when will we launch a spacecraft designed from top down to studying nearby interstellar space? The answer may well be a mission to the Sun's gravity focus. Located at 550 AU (3.17 light days), some 14 times farther from the Sun than Pluto, the focus is that point to which the Sun's gravity bends the light from objects on the other side of it. The effect is to magnify distant images in ways that could be observed using the proper equipment. The effect of gravitational focus, first studied by Einstein in 1936, had already borne observational fruit by 1978 in the discovery of a 'twin...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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