I notice that the question of 'when to launch' has surfaced in comments to my first piece on Interstellar Probe, the APL study to design a spacecraft that would be, in effect, the successor to Voyager. It's a natural question, because if a craft takes 50 years to reach 1000 AU, there will likely be faster spacecraft designed later that will pass it in flight. I'm going to come down on the side of launching as soon as possible rather than anticipating future developments. Two reasons: The research effort involved in stretching what we can do today to reach as high a velocity as possible inevitably moves the ball forward. We learn as we go, and ideas arise in the effort that can hasten the day of faster spacecraft. The second reason is that a vehicle like Interstellar Probe is hardly passive. It does science all along its route. By the time it reaches 1000 AU, it has returned massive amounts of information about the interstellar medium, our Sun's passage through it, and the heliosphere...

Our doughty Voyager 1 and 2, their operations enabled by radioisotope power systems that convert heat produced by the decay of plutonium-238 into electricity, have been pushing outward through and beyond the Solar System since 1977. Designed for a four and a half year mission, we now have, more or less by accident and good fortune, our first active probes of nearby interstellar space. But not for long. At some point before the end of this decade, both craft will lack the power to keep any of their scientific instruments functioning, and one great chapter in exploration will close. What will the successor to the Voyagers look like? The Johns Hopkins University Applied Physics Laboratory (JHU/APL) has been working on a probe of the local interstellar medium. We're talking about a robotic venture that would be humanity's first dedicated mission to push into regions that future, longer-range interstellar craft will have to cross as they move far beyond the Sun. If it flies, Interstellar...

Near-Earth Asteroid Scout (NEA Scout) is a CubeSat mission designed and developed at NASA's Marshall Space Flight Center in Huntsville and the Jet Propulsion Laboratory in Pasadena. I'm always interested in miniaturization, allowing us to get more out of a given payload mass, but this CubeSat also demands attention because it is a solar sail, the trajectory of whose development has been a constant theme on Centauri Dreams. And while NASA has launched solar sails before (NanoSail-D was deployed in 2010), NEA Scout moves the ball forward by going beyond sail demonstrator stage to performing scientific investigations of an asteroid. As Japan did with its IKAROS sail, the technology goes interplanetary. Les Johnson (MSFC) is principal technology investigator for the mission: "NEA Scout will be America's first interplanetary mission using solar sail propulsion. There have been several sail tests in Earth orbit, and we are now ready to show we can use this new type of spacecraft propulsion...

With NASA announcing that its Discovery program would fund both Davinci and Veritas, two missions to Venus, it's worth pausing to consider where we are in the realm of Solar System exploration. This is not to knock the Venus decisions; this is a target that has been neglected compared to, obviously, Mars, and we've kept it on the back burner while exploring Jupiter, Saturn and, with a fast flyby, Pluto/Charon. With budgets always tight, the axe must fall, and fall it has on the promising Trident. Discovery-class involves small-scale missions that cost less than $500 million to develop. The Trident mission would have delivered imagery from Triton that upgraded the 1989 images from Voyager 2, useful indeed given the moon's active surface, and we might have learned about the presence of a subsurface ocean. I should also mention that we lost IVO when the four candidate missions were pared down to two. IVO (Io Volcano Observer) had a strong case of its own, with close flybys of the...

I see that a white paper on Richard Linares' interesting 'statite' concept became available just before Christmas, and I want to call your attention to it (and thanks to Antonio Tavani for the pointer). Back in April, the idea received funding as a Phase 1 study in the NASA Innovative Advanced Concepts (NIAC) Program, renewing attention on the matter of interstellar objects (ISO) like 'Oumuamua. The notion is to deliver a payload to an object discovered entering our Solar System so that, unlike the two we've found thus far ('Oumuamua and 2I/Borisov), we can examine them up close before they depart. Statites are to be the enabling technology. So let's circle back to that concept, for statites are getting more interest these days given the plans for Solar Cruiser, NASA's solar sail mission that may experiment with maneuvers that allow it to act in non-Keplerian ways. The idea is that a solar sail can achieve 'station-keeping' -- hovering in place -- by using light pressure from the Sun...

Our recent discussions about Claudio Maccone's FOCAL mission to the Sun's gravitational focus, and the ongoing work at the Jet Propulsion Laboratory for NASA's Innovative Advanced Concepts office, have had Alex Tolley thinking about alternative scenarios. Yes, a spacecraft moving along the focal line extending from the solar gravitational lens (SGL) would be capable of extraordinary imaging, and could serve as a communications relay for interstellar probes, but that tricky Sundiver maneuver suggested by Slava Turyshev and team in their 'string of pearls' concept puts huge demands on sail materials. Moreover, we'd ideally like to be able to slow the craft as it moves along the focus, to allow maximum time for observations. To achieve both fast transit and maneuverability at the gravitational focus, Alex advocates beamed propulsion, a method whose advantages and consequences are discussed below. Synergies with the ongoing Breakthrough Starshot effort are apparent. by Alex Tolley The...

Getting a probe to another star is a big enough problem, but woven inextricably through it is the issue of communications. Adding payload steepens the propulsion curve in dramatic fashion, which is why recent thinking has dwelled so firmly on miniaturizing the spacecraft. Thus Breakthrough Starshot, which envisions payloads roughly on the order of a computer chip. No wonder, with spacecraft of that size, getting data back to Earth is such a daunting challenge. Can gravitational lensing help? We've seen that the Sun's mass shapes spacetime around it, bending light from targets on the other side so that electromagnetic waves come to a focal point about 550 AU out. The implications for imaging are under intense study at the Jet Propulsion Laboratory, where Slava Turyshev's team, working with a Phase III NIAC grant, is exploring "Direct Multipixel Imaging and Spectroscopy of an Exoplanet with a Solar Gravitational Lens Mission," taking two prior studies, a Phase I and II at NIAC, forward...

In the early summer of 2005, I found myself, thanks to the efforts of Greg Matloff and Princeton's Ed Belbruno, in Princeton for a conference called New Trends in Astrodynamics and Applications II, which Dr. Belbruno had organized. I was to give a brief talk at the end of the session summarizing what was going on in the interstellar travel community. Two days of chill rain didn't dampen my enthusiasm at seeing Greg and his wife, the artist C Bangs, as well as Belbruno himself, who had been a great help as I put together my Centauri Dreams book. And on the morning of the first day of the conference, I joined Greg, C and Claudio Maccone for breakfast at the Nassau Inn, Princeton's lovely colonial era hostelry. I've since had the opportunity to talk with Dr. Maccone many times at conferences, and one year enjoyed memorable meals with him in the Italian Alps, but that first encounter really sticks in my mind. I had been thinking about gravitational lensing for several years, but it was...

It's reassuring to hear that we're in two-way contact once again with Voyager 2. Since last March, controllers have been limited to receiving X-band (8 to 12 GHz) downlink data, with no capability to uplink commands to the craft via S-band (2 to 4 GHz). This has been a problem unique to Voyager 2 thanks to its trajectory. The Deep Space Network's three radio antenna facilities -- Canberra, Australia; Goldstone, California and Madrid, Spain -- are positioned so that at least one facility is available for communications with our far-flung space probes. While Voyager 1 can talk to us via the two northern hemisphere DSN stations, Voyager 2's close flyby of Neptune's large moon Triton in 1989 bent its course well south of the ecliptic. 18.8 billion kilometers from Earth, Voyager 2 can only line up on Canberra, and the antenna called Deep Space Station 43 (DSS43) has been the only southern hemisphere dish with a transmitter capable of reaching the craft at the right frequency to send...

I can think of more than one way to get a good look at the Sun's polar regions. After all, we've done it before, through the Ulysses spacecraft, which passed over the Sun's north and south poles in 1994-1995. A gravity assist at Jupiter was the key to the mission, allowing Ulysses to arc out of the ecliptic and inward to the Sun. But Ulysses lacked the kind of remote-sensing instruments we'd like to use to compile an extensive dataset on the polar magnetic field and, as Don Hassler (SwRI) adds, "the surface/sub-surface flows" we might find in the polar regions. It's good to see a mission designed for that purpose. For Hassler is principal investigator on a concept that has just been approved for further study by NASA, with the haunting name Solaris. I say 'haunting' because it's hard for this Stanislaw Lem reader to forget the novel of the same name, published in 1961, that explores the implications of a vast intelligence on a planet far from Earth. I realize this has been done as a...

Get ready for the Polarimeter to UNify the Corona and Heliosphere (PUNCH) mission, which will begin popping up even as Centauri Dreams continues to consider heliophysics in relation to proposed missions far beyond the Solar System. We've seen recently that the Applied Physics Laboratory at Johns Hopkins is looking, under the leadership of Ralph McNutt, at a mission to 1000 AU, using an Oberth maneuver at the Sun as a possible way to reach such distances with a flight time of 50 years (see The 1000 AU Target). Thus do heliophysics and deep space intersect in unexpected ways, and not just at APL but JPL and elsewhere as we look toward the upcoming decadal survey. As for PUNCH, it's all about the solar wind and the connection between it and the Sun's corona, says PUNCH principal investigator Craig DeForest of Southwest Research Institute's Space Science and Engineering Division: "For over 50 years, we've studied the solar corona by remote imaging and the solar wind by direct sampling....

One reason I wanted to run yesterday's article about the Opher et al. paper on the heliosphere, aside from its innate scientific interest (and it is a very solid, well crafted piece of work) is to illustrate how much we still have to learn about the balloon-like bubble carved out by the solar wind. The entire Solar System fits within it easily, but we observe only from inside and have little knowledge of its structure. None of the paper's authors would argue that we have the definitive answer on the shape of the heliosphere. That will take a good deal more data, as the paper notes: Future remote-sensing and in situ measurements will be able to test the reality of a rounder heliosphere. In Fig. 6, we show our prediction for the interstellar magnetic field ahead of the heliosphere at V2. In addition, future missions such as the Interstellar Mapping and Acceleration Probe will return ENA [energetic neutral atom] maps at higher energies than present missions and so will be able to...

We have all too little information about the heliosphere, the only data from beyond it being what we have collected from the two Voyagers. Altogether, only five spacecraft -- Pioneer 10 and 11, the Voyagers and New Horizons -- have escaped the gravity of the Sun enroute to interstellar space. To understand how the heliosphere operates, and the interactions between the solar wind of charged particles and magnetic fields with what lies beyond, we’d really like to be able to look back at our system in its entirety. The Interstellar Probe concept being pondered at Johns Hopkins Applied Physics Laboratory and elsewhere is one possible way to do this. I’ll have more to say about Interstellar Probe in coming days, though I do want to give a nod to its history, which can be traced as far back as 1958 and a report from the National Academy of Sciences. APL’s Ralph McNutt has been studying interstellar concepts for decades, and was a major source as I worked on my original Centauri Dreams...

Centauri Dreams rarely looks at Mercury, the operative method being generally to focus on the outer Solar System and beyond. But a new paper out of the Planetary Science Institute in Tucson (AZ) raises the eyebrows in suggesting that parts of Mercury may once have been able to shelter prebiotic chemistry and perhaps, according to the authors, even primitive life forms. Such a finding might thus extend our ideas of ‘habitable zones’ much closer to parent stars than previously assumed. It seems a long shot, given surface temperatures reaching 430? in the daytime and -180? at night, but the PSI work turns up interesting possibilities in some subsurface regions of Mercury. The heart of this research is found in the datasets returned by the MESSENGER (MErcury Surface Space ENvironment GEochemistry and Ranging) spacecraft. The Mercury orbiter identified numerous volatile-bearing surfaces on Mercury, with high abundances of sulfur, chlorine and potassium, and polar ice in permanently...

With the James Webb Space Telescope now declared 'a fully assembled observatory' by NASA, environmental tests loom for the instrument, which is now slated for launch in March of 2021. Within that context, we need to place WFIRST (Wide-Field Infrared Space Telescope), whose development was delayed for several years because of cost overruns on JWST. Recall that WFIRST was the top priority for a flagship mission in the last astrophysics Decadal Survey. The good news is that NASA has just announced that WFIRST has passed what it is calling 'a critical programmatic and technical milestone,' which opens the path to hardware development and testing. With a viewing area 100 times larger than the Hubble instrument, WFIRST will be able to investigate dark energy and dark matter while at the same time examining exoplanets by using microlensing techniques applied to the inner Milky Way. Its exoplanet capabilities could be significantly extended if additional budgeting for a coronagraph -- which...

The fault protection routines programmed into Voyager 1 and 2 were designed to protect the spacecraft in the event of unforeseen circumstances. Such an event occurred in late January, when a rotation maneuver planned to calibrate Voyager 2's onboard magnetic field instrument failed to occur because an unexpected delay in its execution left two systems consuming high levels of power (in Voyager terms) at the same time, overdrawing the available power supply. We looked at this event not long after it happened, and noted that within a couple of days, the Voyager team was able to turn off one of the systems and turn the science instruments back on. Normal operations aboard Voyager 2 were announced on March 3, with five operating science instruments that had been turned off once again returning their data. Such autonomous operation is reassuring because Voyager 2 is now going to lose the ability to receive commands from Earth, owing to upgrades to the Deep Space Network in Australia. This...

Centauri Dreams reader Charley Howard recently wrote to ask about how NASA goes about setting its mission priorities and analyzing mission concepts like potential orbiter missions to the ice giants. It's such a good question that I floated it past Ashley Baldwin, who is immersed in the evolution of deep space missions and moves easily within the NASA structure to extract relevant information. Dr. Baldwin had recently commented on ice giant mission analysis by the Outer Planets Advisory Group. But what is this group, and where does it fit within the NASA hierarchy? Here is Ashley's explanation of this along with links to excellent sources of information on the various mission concepts under analysis for various targets, and a bit of trenchant commentary. By Ashley Baldwin Each of the relevant NASA advisory groups has its own page on the NASA site with archives stuffed full of great presentations. The most germane to our discussion here is the Outer Planets Assessment Group (OPAG). My...

Are missions to the Sun particularly relevant to our interstellar ambitions? At the current state of our technology, the answer is yes. Consider Solar Cruiser, which is the planned NASA mission using a solar sail that could maintain non-Keplerian orbits, allowing it to investigate the Sun's high latitudes. And throw in the European Space Agency-led Solar Orbiter, which left our planet early Monday (UTC) on a United Launch Alliance Atlas V rocket, lifting off from Launch Complex 41 at Cape Canaveral Air Force Station in Florida. Herewith the gorgeous arc of ascent: Image: Launch of the ESA/NASA Solar Orbiter mission to study the Sun from Cape Canaveral Air Force Station in Florida on Feb. 9, 2020. Credit: Jared Frankle. Missions to the Sun allow us to explore conditions close to a star and, significantly, deep in its gravity well, where interesting things can happen. When we discuss one way of propelling a sail beyond the heliosphere, the irony is that an Oberth maneuver, which takes...

When one of our Voyagers experiences a blip of any kind, it gets my attention. It's not like we have any other options outside the heliosphere right now. Both Voyagers have fault protection software that allows the spacecraft to protect themselves if problematic situations occur. And a problem did indeed surface aboard Voyager 2 on January 25, when there seems to have been a delay in the onboard execution of commands for a scheduled maneuver. The latter was a 360 degree rotation to be executed as a way of calibrating the craft's magnetic field instrument, and the result of the delay was that two systems that consume power at relatively high levels were operating at the same time. Not a good idea. Right now, with power dwindling inexorably, the Voyager missions are both dominated by power management. Hence the shutdown of Voyager 2's science instruments to make up for the power deficit, as reported by the Voyager team on Twitter: Here's the skinny: My twin went to do a roll to...

We’re seeing our final images of asteroid Ryugu as the Hayabusa2 spacecraft leaves its orbit some 300 million kilometers from Earth. The Japanese Aerospace Exploration Agency (JAXA) intends to keep taking images of the receding Ryugu for several more days, after which it will be necessary to perform an attitude control maneuver to orient the craft for proper operation of its ion engines. An ion engine test period will culminate in cruise operations on December 3 to return the spacecraft to Earth. Image: Asteroid Ryugu captured with the Optical Navigation Camera - Telescopic (ONC-T) immediately after departure. Image time is November 13 10:15 JST (onboard time), 2019. Credit: JAXA, Chiba Institute of Technology, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Meiji University, University of Aizu, AIST. Happily, we are asked to join in JAXA’s ‘Goodbye Ryugu’ campaign by sending a #Sayonara_Ryugu tweet (https://twitter.com/haya2e_jaxa), although the agency...