- 3970 - TELESCOPES - working together? What’s possible when Earth and space-based telescopes work together? The potential benefits of coordinating ground, orbital and in situ based observations of objects can benefit from the type of coordinated output that can only come from a cohesive team.
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----------------------- 3970
- TELESCOPES -
working together?
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- It takes many
telescopes working together. The
different wavelengths contained in the electromagnetic spectrum need to be captured
for the full width of to truly understand some transient phenomena.
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- The
electromagnetic spectrum is extremely large.
It includes all types of light, such as radio, infrared, x-rays,
ultraviolet and visible light. There is
no one single sensor that can collect data in all of those different
wavelengths at the same time.
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- Therefore,
scientists have developed a plethora of instruments that are extremely good at
collecting data in one specific spectrum, such as radio (ALMA), or mid-range
infrared (James Webb).
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- The down
side of this specialization is that those instruments are blind in other
spectral ranges. If a scientific team is
only observing in one type of light, there is a chance that they could miss
important aspects of a phenomena they are studying that are only visible in a
different spectral band.
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- Much of the
planetary science data collected is the result of spacecraft that are sent to a
planetary system to perform in situ observations. However, due to the high cost of developing
space-based systems and then launching them into orbit, mission planners for
these in situ missions must be very selective about what types of instruments
they allow on board their spacecraft.
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- What this
normally means is that they are not able to bring imagers that are capable of
covering the entire electromagnetic spectrum.
That is where coordination with ground and near-earth-orbit based
telescopes comes in.
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- There are
many telescopes in those locations, such as the Atacama desert or Hawaii’s
Mauna Kea, that are extremely large, and can provide very high resolution
images in specific spectral bands, such as radio, microwaves, or infrared.
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- Infrared is
particularly useful as there is a lot of physical data points that can be
obtained in a single measurement, such as pressure, temperature, and molecular
abundances.
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- If a
mission planner of a planetary exploration spacecraft mission can coordinate
observations with these much larger, specialized observatories, they will no
longer need to include them on their own spacecraft.
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- Another
advantage that earth-based observatories have over their in situ counterparts
is their ability to image a whole planet at once. Many orbiter or fly by missions are only capable
of measuring part of their subject at a single point in time.
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- This results
in a loss of contextual understanding, as dynamic phenomena that might be
observed in a single place by the in situ spacecraft might not be present over
the entire surface of the planet or moon.
Support from earth-based telescopes, whether on the ground or in space,
could provide that larger context that the spacecraft itself lacks.
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- One in situ
planetary mission is the Juno spacecraft currently in orbit around Jupiter. The resulting coordination between the Juno
spacecraft and a series of earth-based observatories resulted in over 40 papers
that used data from more than one observational source of the Jupiter system
during that time.
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- Mars is of
particular interest, as it is the most studied planet outside of Earth, and the
only one with active rovers physically on its surface. Scientists interested in understanding where
the methane from Mars’ atmosphere comes from would certainly benefit from a
coordinated observational campaign between several of the orbiters around Mars
(TGO and MAVEN), and earth-based telescopes such as NASA’s Infrared Telescope
Facility in Hawaii.
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- The
orbiters around Mars provide excellent two-dimensional slices of spectral data
as they are passing over a specific strip of the planet. However, observatories closer to Earth can
provide data on the entire hemisphere of the planet that is facing them, and
add a layer of depth that would allow scientists to piece together a three-dimensional
picture that would be impossible using only data from the orbiters.
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- There are
still some limitations to earth-based observations, such as the fact that
methane is present in Earth’s atmosphere as well, which could skew the data
when looking at Mars.
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- To get
around this problem, scientists came up with an ingenious method of only
observing Mars while it is moving away from (or toward) Earth at more than 13km
a second. This differential speed red-
(or blue-) shifts the spectral signature of the Martian methane enough that it
can be differentiated from that simply present in Earth’s atmosphere.
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- Another
particularly interesting target of joint observations is Titan, which has been
the subject of intense scrutiny in recent years due to its hydrocarbon lakes,
and its methane/ethane based hydrological cycle.
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- The moon is
so interesting it is about to receive it’s own in situ visitor in the form of
the “Dragonfly mission”. When Dragonfly
lands in 2034 many Earth-based telescopes will turn their eyes toward Titan, as
the data collected from the surface can then be coordinated with more remote
observations.
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- Dragonfly
will be equipped a mass spectrometer, which allows the detection of molecules
which are impossible to see remotely, and reveals the full composition of the
atmosphere. Earth-based observation
could in turn provide context for these measurements.
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- ALMA is a
series of radio telescopes, which are particularly good at observing organic
compounds and making detailed maps of its observational subjects. Both capabilities would be particularly
helpful in helping the Dragonfly mission, and ALMA’s operators are already very
familiar with Titan.
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April 22, 2023 TELESCOPES -
working together?
3970
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--------------------- --- Sunday, April 23, 2023
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