Page 34 - Astronomy - October 2017 USA

Incredibly, a few instruments aboard both spacecraft continue to function. by John Wenz

Voyager 1 plasma wave science 0.15

Voyager 1 Termination shock
3 0.10 Density (cm -3 )

Interstellar Bow shock Sun Heliosphere Frequency (kHz)
space
0.05
2
Voyager 2 May 1
Nov 1 Jan 1 Mar 1 2013
2013
2012 2013
Above: Voyager 1’s Plasma Wave Science instrument
Above: Voyager had a Cosmic Ray Subsystem to monitor this radiation as it passed measured the bursts of energy seen in this image,
all but confirming the spacecraft had finally entered
through the crafts. An increase showed the escape of both craft from the termination
interstellar space, where the Sun’s magnetic fields end.
shock, where solar wind particles travel at speeds less than that of sound. Voyager 1
crossed this threshold in 2003. Voyager 2 crossed in 2007. The heliosphere is the entire
bubble-shaped region where the Sun has its greatest influence. ASTRONOMY: ROEN KELLY Voyager 1 still has a few thousand years to go before
exiting the solar system entirely. NASA/JPL
Right: Two engineers install the Golden Record, an
encapsulation of humanity as it was in the mid-1970s.
Voyager 1’s final image was the famous This LP-sized object represents a message from Earth to
“Pale Blue Dot” photo. The craft looked whomever may find the probe. The record’s cover shows
back at the solar system, with Earth where the spacecraft came from. The Voyagers will not
appearing as a small dot. Carl Sagan encounter other stars for tens of thousands of years.
conceived of the image; Candy Hansen This may turn out to be a last message from humanity
and Carolyn Porco took it. NASA/JPL-CALTECH should our civilization come to an end. NASA

KEY FINDING: The PPS instrument 8.
KEY FINDING: This instrument gath- discovered a more detailed structure
1. ered the bulk of the data regarding to Uranus’ and Neptune’s ring systems, SHUTDOWN DATE: Essentially never
SHUTDOWN DATE: Still active planetary atmospheres, helping estab- including discovering additional rings PURPOSE: Protect the instruments
PURPOSE: Communications lish what the gas giants were made of in each. at the rear of the craft from dust and
KEY FINDING: This is the craft’s main — and that Uranus and Neptune were other particles that could interfere
contact point with Earth. It once sent different from Jupiter and Saturn in with their operations.
back the robust data from the craft; to- composition. 6. KEY FINDING: Unknown, but it may
day, it sends out basic information from have spared the craft plenty of head-
the low-power instruments still online. SHUTDOWN DATE: Still active aches from tiny particles.
4. PURPOSE: Measure ions and their dis-
tribution in the outer solar system.
2. KEY FINDING: A violent burst of 9.
solar activity in 1993, coupled with
SHUTDOWN DATE: 1998 the Low-Energy Charged Particle SHUTDOWN DATE: Still active
PURPOSE: Monitor temperature and
SHUTDOWN DATE: Still active other information inside the planets. Instrument, helped researchers locate PURPOSE: Help calibrate the craft’s
PURPOSE: Measure the magnetic fields KEY FINDING: The IRIS instrument the heliopause. charged particle instrument, infrared
of the Sun and the outer planets. discovered a heat source deep within radiometer, and cameras.
KEY FINDING: In 2015, the craft discov- Neptune that leaves the planet roughly 7. KEY FINDING: Voyager’s instruments
ered that even past the heliopause, solar the same temperature as Uranus. This SHUTDOWN DATE: Still active pointed to the target plate for calibra-
winds can redirect the magnetic field of is likely due to slightly higher methane PURPOSE: Propel the craft and keep tion countless times in its travels.
charged particles they encounter. content trapping more heat and mak-
ing the planet a few degrees warmer. it warm. 10.
KEY FINDING: While Voyager 1 was in
3. transit to the outer solar system, the
Pioneer 11 craft revealed a substantial
5. atmosphere on Saturn’s moon Titan.
SHUTDOWN DATE: 1998 Rather than steer toward a possible SHUTDOWN DATE: 2008
PURPOSE: Monitor the composition of SHUTDOWN DATE: 1991 encounter with Pluto, NASA used the PURPOSE: Measure radio emissions
planetary atmospheres in ultraviolet PURPOSE: Gather information on craft’s thrusters to send it toward Titan, from the gas giants.
wavelengths, which also show solar the gas giants while monitoring their eventually flinging Voyager 1 above
interaction. atmospheres. the plane of the solar system.
34 ASTRONOMY • OCTOBER 2017