After 37 years of deep sleep, a set of thrusters aboard the Voyager 1 spacecraft, 21 billion km away, were successfully fired up on Wednesday, Nov 29. They will help augment the primary thrusters which are getting old and weak.
Voyager 1, launched in September 5, 1977, now flying in interstellar space, relies on thrusters that are fired for short millisecond periods to subtly rotate the spacecraft and point its communications antenna at Earth.
Since 2014, NASA engineers have noticed that Voyager’s "attitude control thrusters" have been degrading and losing efficiency, producing lower amounts of thrust per firing. Which means that the thrusters will run out of fuel earlier than anticipated.
The Voyager team assembled a group of propulsion experts to study the problem. The solution that came up with was to use the four Trajectory Correction Maneuver (TCM) thrusters, which were originally used for orientation control when Voyager flew by planets and moons during the first few years of its mission. The TCM thrusters are identical in size and functionality to the attitude control thrusters, and are located on the back side of the spacecraft. The TCM thrusters were last used on November 8, 1980, when Voyager 1 flew by Saturn. Back then, the TCM thrusters were used in a more continuous firing mode; they had never been used in the pulse mode necessary for its new role.
On Tuesday, Nov. 28, 2017, Voyager engineers sent instructions to fire up the four TCM thrusters. It took 19 hours and 35 minutes for the signal to reach Voyager 1 and another 19 hours and 35 minutes for the response to arrive. The received signals indicated that everything went according to plan — after 37 years of deep sleep in cold dark space, the thrusters worked perfectly!
Kudos to the designers of the spacecraft and the mission team, who pored through decades-old data and outdated assembler language software to figure out and implement the solution.
The plan going forward is to switch to the TCM thrusters in January. To make the change, Voyager has to turn on one heater per thruster, which requires power -- a limited resource for the aging mission. When there is no longer enough power to operate the heaters, the team will switch back to the attitude control thrusters.
The thruster test went so well, the team will likely do a similar test on the TCM thrusters for Voyager 2, the twin spacecraft of Voyager 1. The attitude control thrusters currently used for Voyager 2 are not yet as degraded as Voyager 1's.
More details at www.nasa.gov/...
Voyager 1
Voyager 1 was launched by NASA on September 5, 1977, to study the outer Solar System. Its twin Voyager 2 was launched 16 days earlier.
The Voyager 1 mission included flybys of Jupiter, Saturn and Saturn's large moon, Titan. It completed its primary mission with the flyby of Saturn on November 20, 1980.
A few vital statistics -
Parameter |
Value |
Distance |
141 AU (2.11×1010 km) from Sun
AU = Astronomical Unit = average Earth-Sun distance = ~150 million km
|
Speed |
38,026 mph
520 million km per year
|
Communications Delay (one-way) |
19 hours and 35 minutes |
Launch Date |
September 5, 1977 |
Power |
3 radioisotope thermoelectric generators
470 W at launch time
Plutonium-238 left = 72.76%. Will decline to 56.5% by 2050.
|
Computers |
3 subsystems, each with a pair of processors
Custom 16-bit designs
|
RAM |
69.63 kilobytes, across all 6 computers. www.wired.com/…
(A smart phone has 1 to 2 Gigabytes of RAM)
|
Flight Data computer Processor speed |
81,000 instructions per second
(A smart phone does around a few billion instructions per second)
|
Communications link speed |
160 bits per second
(A FIOS connection runs somewhere between 25 and 100 Mbps)
|
Secondary storage |
Digital ½ inch 8-track tape :-) Capacity = 536 million bits
Uses error correction codes
|
Here is a diagram of Voyager 1 and its instruments -
Here is an animation showing the trajectory of the two Voyager spacecraft -
Voyager 1 is in "Interstellar space" and Voyager 2 is currently in the "Heliosheath" -- the outermost layer of the heliosphere where the solar wind is slowed by the pressure of interstellar gas. See voyager.jpl.nasa.gov/… for some more fun facts about Voyager.
For the next 10 years, the Voyagers will be making measurements of interstellar material, magnetic fields and cosmic rays along their trajectories. In about 40,000 years, Voyager 1 will pass within 1.6 light-years of the star Gliese 445, in the constellation Camelopardalis. Long before that, the spacecraft will lose its energy source and shut down all instruments. Voyager 2, is now 10.5 billion miles from Earth, and will pass 1.7 light-years from the star Ross 248 in about 40,000 years. www.nasa.gov/…
Here is a new video highlighting
Voyagers' epic journey through the solar system -
The Golden Record
Each Voyager spacecraft carries a gold-plated audio-visual disc intended for any intelligent life forms out there. The disc carries encoded photographs, music, sounds and greetings in 55 languages. See picture below of the record cover.
See voyager.jpl.nasa.gov/… for a fascinating description of the images and the playback instructions encoded in them. An excerpt is shown below -
In the upper left-hand corner is an easily recognized drawing of the phonograph record and the stylus carried with it. The stylus is in the correct position to play the record from the beginning. Written around it in binary arithmetic is the correct time of one rotation of the record, 3.6 seconds, expressed in time units of 0,70 billionths of a second, the time period associated with a fundamental transition of the hydrogen atom. The drawing indicates that the record should be played from the outside in. Below this drawing is a side view of the record and stylus, with a binary number giving the time to play one side of the record - about an hour.
The record is a classic phonograph audio record using a gold plated copper disk. All data is encoded as sound! It requires some sophisticated processing (by the sophisticated aliens) to decode the data and extract images, music, greetings, etc. See this page boingboing.net/… for some info on the decoding process.
Here is a fascinating real-time decoding of images from the disk done by the author at boingboing.net/...
Voyager 1 and 2 both carry this record. There are ten more on display at various NASA institutions. Even Carl Sagan, who chaired the committee that created the record, did not get a copy. The record was never made available to the general public.
Now we can get a 3 LP box set of the decoded record for $98, thanks to a Kickstarter-funded project . Also, available as a 2 CD set at lightintheattic.net/… for $50. Both versions come with a hardcover illustrated book.
Here is video containing decoded information from the record -
Remarks
After 40 years, each Voyager spacecraft is still going strong, having survived the rigors of space over its 21.1 billion km journey. Made possible by the ingenuity and hard work of its designers and mission personnel. A mission that has inspired generations of engineers and scientists. We need more investment of minds and dollars in such programs, not less.
To paraphrase D. H. Lawrence,
They say space is cold, but space contains
the hottest blood of all, and the wildest, the most urgent
All the spaceships in the wider orbits, hot are they, as they urge
on and on, and dive between the planets.
The Voyagers, the Pioneers, the New Horizons, the Cassinis,
there they blow, there they blow, hot wild white breath out of the vacuum!
What memories do you have of the time when the Voyager spacecraft were launched? And what do you see in the future of humankind?
References
- Voyager program — en.wikipedia.org/…
- Voyager 1 wiki — en.wikipedia.org/…
- Voyager NASA site — voyager.jpl.nasa.gov
- Computers in Spaceflight: The NASA Experience- history.nasa.gov/…
- Voyager backgrounder — ntrs.nasa.gov/...