The Arecibo Radio Telescope. Though it's decommissioned now, Arecibo Data may explain 1977's mysterious Wow! Signal. Image Credit: UCF
This past summer, the Arecibo Observatory suffered major damage when an auxiliary cable that supports the platform above the telescope broke and struck the reflector dish. Immediately thereafter, technicians with the observatory and the University of Central Florida (UCF) began working to stabilize the structure and assess the damage. Unfortunately, about two weeks ago (on Nov. 6th), a second cable broke causing even more damage.
Following a thorough review, the U.S. National Science Foundation (NSF) announced that the observatory cannot be stabilized without risking the lives of construction workers and staff at the facility. As such, after 57 years of faithful service and countless contributions to multiple fields of astronomy, the NSF has decided to commence plans for decommissioning the Arecibo Observatory.
The Arecibo Radio Telescope. Though it's decommissioned now, Arecibo Data may explain 1977's mysterious Wow! Signal. Image Credit: UCF
On Aug. 10th, a little over a month ago, the iconic Arecibo Observatory suffered serious damage when an auxiliary cable broke and struck the reflector dish. This cable struck the observatory’s Gregorian Dome on its way down and twisted an access platform before landing on the reflecting dish itself. The impact created a gash over 30 meters (100 feet) in length and forced the observatory to shut down until repairs could be made.
Since then, teams have been busy working to stabilize the structure and determine the cause. These teams are made up of technicians from the observatory and the University of Central Florida (UCF), which manages the facility for the National Science Foundation (NSF). For the past few weeks, they have been meeting with experts from various fields and laying the groundwork for an investigation and a rigorous repair schedule.
When a star reaches the end of its life cycle, it will blow off its outer layers in a fiery explosion known as a supernova. Where less massive stars are concerned, a white dwarf is what will be left behind. Similarly, any planets that once orbited the star will also have their outer layers blown off by the violent burst, leaving behind the cores behind.
For decades, scientists have been able to detect these planetary remnants by looking for the radio waves that are generated through their interactions with the white dwarf’s magnetic field. According to new research by a pair of researchers, these “radio-loud” planetary cores will continue to broadcast radio signals for up to a billion years after their stars have died, making them detectable from Earth.
The Karl G. Jansky Very Large Array, located in central New Mexico. Credit: NRAO
In July of 2015, Russian billionaire Yuri Milner announced the creation of Breakthrough Listen, a decade-long project that would conduct the largest survey to date for signs of extra-terrestrial communications (ETI). As part of his non-profit organization, Breakthrough Initiatives, this survey would rely on the latest in instrumentation and software to observe the 1,000,000 closest stars and 100 closest galaxies.
Using the Green Bank Radio Telescope in West Virginia, the Listen science team at UC Berkeley has been observing distant stars for over a year now. And less than a week ago, they observed 15 Fast Radio Bursts (FRBs) coming from a dwarf galaxy located three billion light-years away. According to a study that described their findings, this was the first time that repeating FRBs have been seen coming from this source at these frequencies.
The team’s study, titled “FRB 121102: Detection at 4 – 8 GHz band with Breakthrough Listen backend at Green Bank“, was recently published in The Astronomers Telegraph. Led by Dr. Vishal Gajjar – a postdoctoral researcher at the University of California, Berkeley – the team conducted a detailed survey of FRB 121102. This repeating FRB source is located in a dwarf galaxy in Auriga constellation, some 3 billion light-years from Earth.
The NSF’s Arecibo Observatory, which is located in Puerto Rico, is the world largest radio telescope. Credit: NAIC
To clarify, FRBs are brief, bright pulses of radio waves that are periodically detected coming from distant galaxies. This strange astronomical phenomena was first detected in 2007 by Duncan Lorimer and David Narkovic using the Parkes Telescope in Australia. To honor their discovery, FRBs are sometimes referred to as “Lorimer Bursts”. Many FRB sources have been confirmed since then, some of which were found repeating.
The source known as FRB 121101 was discovered back on November 2nd, 2012, by astronomers using the Arecibo radio telescope. At the time, it was the first FRB to be discovered; and by 2015, it became the first FRB to be seen repeating. This effectively ruled out the possibility that repeating FRBs were caused by catastrophic events, which had previously been theorized.
And in 2016, FRB 121102 was the first FRB to have its location pinpointed to such a degree that its host galaxy could be identified. As such, the Listen science team at UC Berkeley was sure to add FRB 121102 to their list of targets. And in the early hours of Saturday, August 26th, Dr. Vishal Gajjar – a postdoctoral researcher at UC Berkeley – observed FRB 121102 using the Green Bank Radio Telescope (GBRT) in West Virginia.
Using the Digital Backend instrument on the GBRT, Dr. Gajjar and the Listen team observed FRB 121102 for five hours. From this, they accumulating 400 terabytes of data in the entire 4 to 8 GHz frequency band which they then analyzed for signs of short pulses over a broad range of frequencies. What they found was evidence of 15 new pulses coming from FRB 121102, which confirmed that it was in a newly active state.
The Green Bank Telescope, located in West Virginia. Credit: NRAO
In addition, their observations revealed that the brightest of these 15 emissions occurred at around 7 GHz. This was higher than any repeating FRBs seen to date, which indicated for the first time that they can occur at frequencies higher than previously thought. Last, but not least, the high-resolution data the Listen team collected is expected to yield valuable insights into FRBs for years to come.
This was made possible thanks to the Digital Backend instrument on the GBRT, which is able to record several GHz of bandwidth simultaneously and split the information into billions of individuals channels. This enables scientists to study the proprieties and the frequency spectrum of FRBs with greater precision, and should lead to new theories about the causes of these radio emissions.
So even if these particular signals should prove to not be an indication of extra-terrestrial intelligence, Listen is still pushing the boundaries of what is possible with radio astronomy. And given that Breakthrough Listen is less than two years into its proposed ten-year survey, we can expect many more sources to be observed and studied in the coming years. If there’s evidence of ETI to be found, we’re sure to find out about it sooner or later!
And be sure to check out this video of the Green Bank Telescope and the surveys it allows for, courtesy of Berkeley SETI:
A graphic illustrating the ISEE-3 spacecraft's history. Courtesy Tim Reyes.
What is it like to make contact with a 36-year old dormant spacecraft?
“The intellectual side of you systematically goes through all the procedures but you really end up doing a happy dance when it actually works,” Keith Cowing told Universe Today. Cowing, most notably from NASA Watch.com, and businessman Dennis Wingo are leading a group of volunteer engineers that are attempting to reboot the International Sun-Earth Explorer (ISEE-3) spacecraft after it has traveled 25 billion kilometers around the Solar System the past 30 years.
Its initial mission launched in 1978 to study Earth’s magnetosphere, and the spacecraft was later repurposed to study two comets. Now, on its final leg of a 30-plus year journey and heading back to the vicinity of Earth, the crowdfunding effort ISEE-3 Reboot has been working to reactivate the hibernating spacecraft since NASA wasn’t able to provide any funds to do so.
The team awakened the spacecraft by communicating from the Arecibo radio telescope in Puerto Rico, using a donated transmitter. While most of the team has been in Puerto Rico, Cowing is back at home in the US manning the surge of media attention this unusual mission has brought.
Those at Arecibo are now methodically going through all the systems, figuring out what the spacecraft can and can’t do.
“We did determine the spin rate of spacecraft is slightly below what it should be,” Cowing said, “but the point there is that we’re now understanding the telemetry that we’re getting and its coming back crystal clear.”
For you tech-minded folks, the team determined the spacecraft is spinning at 19.16 rpm. “The mission specification is 19.75 +/- 0.2 rpm. We have also learned that the spacecraft’s attitude relative to the ecliptic is 90.71 degrees – the specification is 90 +/- 1.5 degrees. In addition, we are now receiving information from the spacecraft’s magnetometer,” Cowing wrote in an update on the website.
The next task will be looking at the propulsion system and making sure they can actually fire the engines for a trajectory correction maneuver (TCM), currently targeted for June 17.
One thing this TCM will do is to make sure the spacecraft doesn’t hit the Moon. Initial interactions with the ISEE-3 from Arecibo showed the spacecraft was not where the JPL ephemeris predicted it was going to be.
“That’s a bit troublesome because if you look at the error bars, it could hit Moon, or even the Earth, which is not good,” Cowing said, adding that they’ve since been able to refine the trajectory and found the ephemeris was not off as much as initially thought, and so such an impact is quite unlikely.
“However, it’s not been totally ruled out, — as NASA would say it’s a not a non-zero chance,” Cowing said. “The fact that it was not where it was supposed to be shows there were changes in its position. But assuming we can fire the engines when we want to, it shouldn’t be a problem. As it stands now, if we didn’t do anything, the chance of it hitting the Moon is not zero. But it’s not that likely.”
But the fact that the predicted location of the spacecraft is only off by less than 30,000 km is actually pretty amazing.
Consider this, the spacecraft has completed almost 27 orbits of the sun since the last trajectory maneuver. That is 24.87 billion kilometers. They are off course by less than 30,000 km. I can’t even come up with an analogy to how darn good that is!! That is almost 1 part in ten million accuracy! We need to confirm this with a DSN ranging, but if this holds, the fuel needed to accomplish the trajectory change is only about 5.8 meters/sec, or less than 10% of what we thought last week!
We truly stand on the shoulders of steely eyed missile men giants..
Dennis Wingo and ISEE-3 Reboot engineers at Arecibo. Image courtesy ISEE-3 Reboot.
In 1982, NASA engineers at Goddard Space Flight Center, led by Robert Farquhar devised the maneuvers needed to send the spacecraft ISEE-3 out of the Earth-Moon system. It was renamed the International Cometary Explorer (ICE) to rendezvous with two comets – Giacobini-Zinner in 1985 and Comet Halley in 1986.
“Bob Farquhar and his team initially did it with pencils on the back of envelopes,” Cowing said, “so it is pretty amazing. And we’re really happy with the trajectory because we’ll need less fuel – we have 150 meters per second of fuel available, and we’ll only need about 6 meters per second of maneuvering, so that will give us a lot of margin to do the other things in terms of the final orbit, so we’re happy with that. But we have to fire the engines first before we pat ourselves on the back.”
And that’s where the biggest challenge of this amateur endeavor lies.
“The biggest challenge will be getting the engines to fire,” Cowing said. “The party’s over if we can’t get it to do that. The rest will be gravy. So that’s what we’re focusing on now.”
After the June 17 TCM, the next big date is August 10, when the team will attempt to put the spacecraft in Earth orbit and then resume its original mission that began back in 1978 – all made possible by volunteers and crowdfunding.
We’ll keep you posted on this effort, but follow the ISEE-3 Reboot Twitter feed, which is updated frequently and immediately after anything happens with the spacecraft. Also, for more detailed updates, check out the SpaceCollege website.
