IMAGE | Wikipedia audio article


IMAGE (Imager for Magnetopause-to-Aurora Global
Exploration) is a NASA Medium Explorers mission that studied the global response of the Earth’s
magnetosphere to changes in the solar wind. It was believed lost but as of August 2018
might be recoverable. It was launched March 25, 2000 by a Delta
II rocket from Vandenberg AFB on a two-year mission. Almost six years later, it unexpectedly ceased
operations in December 2005 during its extended mission and was declared lost. The spacecraft was part of NASA’s Sun-Earth
Connections Program, and during its run had over 400 research articles published in peer-reviewed
journals using its data. It had special cameras that provided various
breakthroughs in understanding the dynamics of plasma around the Earth. The Principal Investigator was Jim Burch of
the Southwest Research Institute. In January 2018, an amateur satellite tracker
found it to be transmitting some signals back to Earth. NASA made attempts to communicate with the
spacecraft and determine its payload status, but has had to track down and adapt old hardware
and software to the current systems. On February 25, contact with IMAGE was again
lost only to be reestablished on March 4, 2018. The signal disappeared once again on August
5, 2018. Recovery efforts are underway and if successful
NASA may decide to fund a restarted mission.==Overview==
IMAGE was the first spacecraft dedicated to imaging the Earth’s magnetosphere. IMAGE was a spacecraft developed by the Medium-Class
Explorers (MIDEX) program, and it was the first spacecraft dedicated to observing the
magnetosphere of the Earth, producing comprehensive global images of plasma in the inner magnetosphere. The IMAGE craft was placed in a 1,000×46,000
km orbit around the Earth, with an inclination of 90° (passing over the poles) and a 14.2
hour period. By acquiring images every 2 minutes in wavelengths
invisible to the human eye, it allowed detailed study of the interaction of the solar wind
with the magnetosphere and the magnetosphere’s response during a magnetic storm. From its distant orbit, the spacecraft produced
a wealth of images of the previously invisible region of space in the inner magnetosphere,
exceeded all its scientific goals. A senior review in 2005, just previous to
its loss, described the mission as “extremely productive”, having confirmed several theoretical
predictions (e.g., plasmasphere plumes, pre-midnight ring-current injection, and continuous antiparallel
reconnection), discovered numerous new and unanticipated phenomena (e.g., plasmasphere
shoulders, subauroral proton arcs, and a secondary interstellar neutral atom stream), and answered
a set of outstanding questions regarding the source region of kilometric continuum radiation,
the role of solar wind pressure pulses in ionospheric outflow, and the relationship
between proton and electron auroras during substorms. When the spacecraft went silent in December
2005, it had already been approved a mission extension until 2010.Costs for IMAGE are estimated
at US$132 million, including the spacecraft, instruments, launch vehicle, and ground operations.==Payload==
Its science payload consists of three suites of instruments:
Energetic neutral atom imagers (LENA, MENA, HENA) — These instruments use hydrogen,
helium, and oxygen atoms in the exosphere to form images and determine the properties
of their low-, medium- and high-energy parent ions. HENA, the High Energy Neutral Atom imager
is a modified version of the MIMI/INCA (Magnetospheric Imaging Instrument/Ion and Neutral Camera)
sensor flown on the Cassini–Huygens mission. Ultraviolet imagers (FUV and EUV) — The
Extreme Ultraviolet (EUV) imager detects light from helium atoms in Earth’s plasmasphere. The Far Ultraviolet (FUV) imager employs three
detectors to image the auroras in different wavelengths and measure the distribution of
different ions. Radio Plasma Imager (RPI) — This instrument
uses pulses of radio waves to image the entire volume of the Earth’s magnetic field. With its 502 meters-long antenna, it sends
out a burst of radio waves, which reflect off of clouds of charged particles between
the plasmasphere’s outer boundary all the way out to the boundary where the Earth’s
magnetic field is impacted by the solar wind. RPI also measures naturally occurring plasma
waves at the spacecraft’s location.The Central Instrument Data Processor (CIDP) as well as
the Command & Data Handling Subsystem (main on-board computer) were built around the mission-proven
IBM RAD6000 avionics processors.==Loss==
On December 18, 2005, the satellite failed to
make an expected contact at 16:20 UTC. An earlier contact had ended successfully
at 07:39 the same day with no sign of trouble. Over the following days and weeks, commands
were sent “blind” to reset the transmitter, change antennas, and otherwise attempt to
re-establish contact with the spacecraft, but no signal (not even an unmodulated carrier
wave) was received. Recovery efforts included using different
DSN antennas, using non-NASA ground stations in case there was some systematic DSN error,
transmitting no commands for several days to trigger a 72-hour watchdog timer, increasing
transmit power in case the antenna was badly misaligned, and optical and radar observations
of the satellite to check for debris, change in spin rate or change in orbit indicative
of a collision or other damage.:16–17The spacecraft was also commanded to slightly
increase its spin rate and asymmetrically turn on its heaters. If observed, these would indicate that it
could receive commands but not transmit. Neither change was seen and analysis later
indicated that the temperature change would have been undetectable. An attempt to observe the craft’s temperature
to determine if it was completely dead or consuming the power expected in safe mode
was inconclusive.:10–11A careful failure analysis revealed that, among plausible causes
for an abrupt bidirectional loss of communication, the Solid State Power Converter (SSPC) for
the transponder had, among its features, an “instant trip” shutdown in response to a high-current
(100 A) short circuit. Critically, such a shutdown was not reported
in the power supply’s telemetry output and this lack was not documented. Because it was undocumented the spacecraft’s
hardware and software had no provision for attempting to reset the SSPC if it reported
good status.:13 This would result in the observed symptoms: no radio communication with an apparently
undamaged spacecraft.:1,12–13,22,29–31Although such a short circuit would be almost impossible
without fatal damage to the spacecraft, the shutdown could be falsely triggered by a radiation-induced
single event upset.:1,30–31 It could be simply fixed by power-cycling the supply,
but the spacecraft design left no way to send such a command, nor was one built in. The same problem with the same model of power
supply had affected the EO-1 and WMAP satellites (launched after IMAGE),:1,13 but they were
able to recover. In January 2006, NASA declared the mission
over, declaring that “Preliminary analysis indicated the craft’s power supply subsystems
failed, rendering it lifeless.” Despite this, they continued to try and establish
contact. In early 2006, NASA convened a board of experts
to figure out what went wrong. After several months they created a report
in which they theorized that IMAGE had tripped a power breaker and might fix itself.It was
hoped that an eclipse when the spacecraft passed through the Earth’s shadow in October
2007 would result in a sufficiently deep supply voltage sag that it would trigger a total
bus reset, which would cause a power cycle of the suspect supply.:14–18 However, attempts
to contact the craft after this eclipse were not successful.==Recovery efforts==
On January 20, 2018 IMAGE was found by Canadian radio amateur and satellite tracker Scott
Tilley to be broadcasting, and he reported it to NASA. He had been scanning the S-band (microwaves)
in the hopes of finding the Zuma satellite.On January 24, 2018 Richard Burley of NASA reported
that they were trying to establish communication with the satellite using the NASA Deep Space
Network. Two days later, Burley reported that engineers
at Goddard Space Flight Center successfully acquired the signal, and confirmed on January
30, 2018 that IMAGE is the source. It is not known when the satellite started
broadcasting, but re-examination of old data recorded by Tilley and fellow satellite tracker
Cees Bassa showed transmissions from the same satellite in October 2016 and May 2017. Bassa hypothesized that while the 2007 eclipse
did not manage to reset the satellite, another one did the trick, probably sometime between
2014 and 2016.On February 8, 2018 NASA published a detailed account of the IMAGE satellite’s
recovery. The satellite was transmitting data beyond
simple telemetry, indicating that some of its six onboard instruments were still active. NASA engineers are attempting to determine
the satellite’s status, but since the software and hardware type used in the IMAGE Mission
Operations Center have been discarded and no longer exist, they are in the process of
adapting old software and databases to their modern systems and track down replacement
hardware.On February 25, 2018 NASA again lost contact with the satellite, but not in the
same manner it did in 2005. Richard Burley, former IMAGE mission director,
stated that he believes there is an issue with IMAGE’s spin axis in relation to its
medium-gain antenna placement. If NASA can regain control of the spacecraft,
and the status of data and ground systems can be assessed, it will decide if it can
fund a mission restart.On March 4, 2018 the Applied Physics Laboratory at Johns Hopkins
University reported detecting the signal from the satellite, but it was too faint to lock
onto.On May 9, 2018 Scott Tilley again detected a strong signal from IMAGE. Hours later NASA and APL engineers had locked
onto the signal and were receiving telemetry. Commands were transmitted to IMAGE, but for
unknown reasons the spacecraft only acknowledged receipt of a fraction of those commands.On
August 28, 2018 NASA announced that the IMAGE team had stopped receiving any signals from
the satellite, as previously happened in winter, and would continue to try sending commands.On
January 20, 2019 a full year passed since the spacecrafts original discovery date and
it remains out of contact since August 5, 2018.==Gallery==
Photos of IMAGE==
See also==Galaxy 15
List of plasma physics articles Magnetospheric Multiscale Mission

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