Thursday, March 21, 2013

Voyager: Looking Backward and Forward

A paper about the Voyager missions was given a headline that announced that Voyager 1 had left the Solar System and then was revised to be a bit less sensational.  Please do read Paul Gilster's blog, a snippet seen below.
- LRK -


Voyager: Looking Backward and Forward

by PAUL GILSTER on MARCH 21, 2013
The Voyager spacecraft have run into their share of problems as they move toward true interstellar space, but on the whole their continued operations have been a testament to what well designed equipment can do. Voyager 2’s camera platform locked for a time not long after the Saturn flyby but controllers were able to restore the system by experimenting with similar actuators on Earth. Three years ago the craft began having data problems resulting from a flipped bit in an onboard computer but a reset from Earth corrected the fault. Even the failure of the primary radio receiver not long after launch was resolved by the use of the onboard backup.
Obviously both craft are living on borrowed time as the power output of their radioisotope thermoelectric generators (RTGs) continues to decline, but we should still be getting signals for another decade or so. With the Voyagers now on what is designated their ‘interstellar mission,’ it’s pleasing to note that Alpha Centauri is the guide star that Voyager 1 used to reorient itself to resume transmissions to Earth following 2011 maneuvering to allow better detection of the solar wind. We continue to push deeper into a region of space that is now little understood.
Leaving the Solar System
Yesterday’s brief skirmish over Voyager 1’s true situation tells us how much we have to learn about the Solar System’s edge. A paper by William Webber (New Mexico State) and the late Frank McDonald (University of Maryland) reported that a sudden change in cosmic rays detected by Voyager 1 last summer showed that the spacecraft was in a new region of the Solar System they called the ‘heliocliff.’ What evidently confused matters was that the American Geophysical Union, publisher of Geophysical Review Letters — the publication at which the paper had been accepted — sent out a news release saying the craft had left the Solar System.
While the cosmic ray changes were marked, with galactic cosmic ray intensity suddenly doubling last August, Caltech’s Ed Stone issued a statement saying that a change in the magnetic field will be the true indication of Voyager 1’s arrival in interstellar space. No such change has yet been detected, and the AGU soon revised the news release headline to say that the spacecraft had ‘entered a new region of space.’ The ‘heliocliff,’ in other words, is apparently the same region that NASA scientists had already noted as a previously unknown ‘highway’ of magnetic particles. Nancy Atkinson straightened all this out quickly on Universe Today.


The American Geophysical Union corrected press release.
- LRK -

Please note that the headline on this release has been changed to better represent the findings reported in the study

Voyager 1 has entered a new region of space, sudden changes in cosmic rays indicate

20 March 2013
AGU Release No. 13-11
For Immediate Release
WASHINGTON – Thirty-five years after its launch, Voyager 1 appears to have travelled beyond the influence of the Sun and exited the heliosphere, according to a new study appearing online today.
The heliosphere is a region of space dominated by the Sun and its wind of energetic particles, and which is thought to be enclosed, bubble-like, in the surrounding interstellar medium of gas and dust that pervades the Milky Way galaxy.
On August 25, 2012, NASA's Voyager 1 spacecraft measured drastic changes in radiation levels, more than 11 billion miles from the Sun. Anomalous cosmic rays, which are cosmic rays trapped in the outer heliosphere, all but vanished, dropping to less than 1 percent of previous amounts. At the same time, galactic cosmic rays – cosmic radiation from outside of the solar system – spiked to levels not seen since Voyager's launch, with intensities as much as twice previous levels.
The findings have been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
"Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere," said Bill Webber, professor emeritus of astronomy at New Mexico State University in Las Cruces. He calls this transition boundary the "heliocliff."
In the GRL article, the authors state: "It appears that [Voyager 1] has exited the main solar modulation region, revealing [hydrogen] and [helium] spectra characteristic of those to be expected in the local interstellar medium."
However, Webber notes, scientists are continuing to debate whether Voyager 1 has reached interstellar space or entered a separate, undefined region beyond the solar system.
"It's outside the normal heliosphere, I would say that," Webber said. "We're in a new region. And everything we're measuring is different and exciting."
The work was funded by NASA's Jet Propulsion Laboratory in Pasadena, Calif.
Notes for Journalists
Journalists and members of the public can download a PDF copy of this accepted article by clicking on this link:
Or, you may order a copy of the final paper by emailing your request to Peter Weiss at Please provide your name, the name of your publication, and your phone number.
Neither the paper nor this press release are under embargo
“Recent Voyager 1 Data Indicate that on August 25, 2012 at a Distance of 121.7 AU From the Sun, Sudden and Unprecedented Intensity Changes were Observed in Anomalous and Galactic Cosmic Rays”
W.R. Webber
New Mexico State University, Department of Astronomy, Las Cruces, New Mexico, USA;
F.B. McDonald
University of Maryland, Institute of Physical Science and Technology, College Park, Maryland, USA. (Deceased)
Contact information for the authors:
W.R. Webber, Email:, Telephone: (575) 646-2007


Los Angeles Times article.
- LRK -


Voyager 1 has left the solar system — almost

The American Geophysical Union announces that the space probe has become the first man-made object to enter interstellar space, only to backtrack when NASA scientists and others dispute the claim.

A NASA illustration depicts one of the twin Voyager spacecraft. NASA scientists Wednesday disputed an announcement that Voyager 1 had moved beyond the solar system and into interstellar space. (NASA /August 9, 2002)

By Monte Morin and Amina Khan, Los Angeles Times
March 20, 20138:09 p.m.

It was welcome news to Earthlings: The Voyager 1 spacecraft had seemingly crossed a momentous threshold and become the first man-made object to enter interstellar space.
"Voyager 1 has left the solar system," the American Geophysical Union declared Wednesday in a news release. An accompanying study published online in the organization's journal, Geophysical Research Letters, also contained an unusually sentimental end note declaring that "we did it. Bon Voyage!"
Alas, the elation that spread through news and social media was short-lived. Voyager 1 was still in the neighborhood,NASA said, even after traveling for more than 35 years. Then the American Geophysical Union press office issued a correction of its headline, omitting any reference to the spacecraft having departed "the solar system."

And at JPL - Voyager - The Interstellar Mission

Thanks for looking up with me.  
- LRK -