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Mission Statement
The DANDE mission will explore the spatial
and temporal variability of the neutral thermosphere at
altitudes of 350 -100 km, and investigate how wind and
density variability over 500 – 3,000 km scales translate to
drag forces on satellites.
Mission Objectives
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Establish and understand the relationship
between total mass density, composition, and winds as
functions of latitude, level of magnetic activity, and
horizontal scale.
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Establish the relative contributions of
density and winds to satellite drag as a function of
latitude, level of magnetic activity, and horizontal scale.
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Demonstrate key technologies for performing
in-situ measurements of the orbital drag environment at low
cost.
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Improve understanding of the variation in
coefficient of drag in the 100-200 km altitude region.
Mission Concept
DANDE's
mission concept is illustrated below:
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Ascent |
Day 0 DANDE will
launch as a secondary payload attached to the upper
stage of a government satellite launch.
Electrical and mechanical inhibits will ensure that
no portion of DANDE becomes active before separation
from the launch vehicle. |
|
Separation |
Day 0 At a
predetermined time and location, DANDE will separate
from the launch vehicle. Once clear of the
launch vehicle, the inhibits will allow DANDE to
power up for the first time since leaving earth. |
|
Safe Mode |
Day 1 When DANDE
powers up, it will automatically enter "Safe Mode."
This mode will allow DANDE to charge its batteries
and respond to ground commands. This mode is
"safe" because DANDE can safely stay in this mode
indefinitely while tumbling (without attitude
control) and charging the batteries. |
|
Aerobraking Deploy |
Days 2-60 Once
DANDE's batteries are charged and the onboard
systems have been checked out from the ground, the
aerobraking "parachute" will deploy. This will
cause DANDE to rapidly descend to 350 km altitude
where it can perform its science mission.
Science operations: periodic instrument checkouts |
|
Aerobraking Jettison |
Day 60 Once DANDE
has descended to 350 km, the aerobraking "parachute"
will be jettisoned, leaving DANDE in the spherical
configuration required for its science mission.
Science operations: accelerometer readings of
separation. |
|
Preparation for Science Mode |
Days 60 - 70 In
order to prepare for science data collection, DANDE
will use electromagnets to spin-stabilize the
spacecraft.
The science instruments will also be tested and
undergo a "bakeout" to drive off contaminants that
might affect readings.
Science operations: instrument checkouts |
|
Science Mode |
Days 70 - 160 During
science mode, the three science instruments will
take data at precise time intervals. This data will
be processed and stored for later downlink.
Science mode will periodically pause so that the
spacecraft can enter safe mode to recharge its
batteries, followed by a brief re-spin operation to
prepare for the next science mode period.
Science operations: full instrument operation |
|
Geomagnetic Storm |
Approximately every
two weeks, a geomagnetic storm will occur.
DANDE will take data both during storm periods, and
during quiet periods, to allow comparison of
atmospheric variations between the two. Science
operations: full instrument operations. |
|
Communications Mode |
DANDE will pass over
its ground station several times a day. During
these short periods (3 - 5 minutes), the ground
station will initiate communications with DANDE,
downlink stored science data, and uplink any
commands and information necessary for the next
period of operations. Science operations: briefly
paused during communications. |
|
Re-Entry Mode |
Days 160 - 170
Towards the end of its 100 day science mission,
DANDE will change to a modes which will allow
precisely measuring its coefficient of drag as it
begins descending rapidly through the atmosphere.
This will continue for as long as possible before
DANDE re-enters the atmosphere.
Science operations: coefficient of drag only. |
Aerobraking Concept
The DANDE
mission will perform in-situ measurement of the upper
atmosphere between 350 km altitude and 100 km altitude.
Because this region of the atmosphere is relatively dense,
the mission is anticipated to last only 100 days before the
spacecraft re-enters the atmosphere and burns up.
Because
DANDE will be a secondary payload, it will have to adapt to
orbit and altitude opportunities that will be made available
on primary payload flights. A significant problem is that few
primary payloads travel to orbits in the above altitude
range, precisely because missions at that altitude don't
last very long. Most missions are to higher altitudes such
as 500 to 600 km. If DANDE were to be released at a
500 km altitude, it would take over 7 years for the orbit to
naturally decay to 350 km where it's science mission could
begin.
To mitigate
this problem, the DANDE team is investigating the use of a
"space parachute" to allow the spacecraft to aerobrake,
or
descend rapidly from a higher orbit. By deploying a
lightweight structure, the drag area of the spacecraft will
be significantly increased, which can reduce the 500 km to
350 km decay time from 7 years to 2 months. Once DANDE
reaches its target altitude the "parachute" module will be
jettisoned, and the science mission will begin.
Because the
"space parachute" adds development risk to the DANDE
mission, it is being developed in parallel with the rest of
the mission system. Whether it is employed or not will
depend on whether it is needed (if a launch to 350 km is
unavailable), and testing of the system provides a high
assurance of success.
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