Problem
Statement
The Korea Meteorological Administration is planning to develop a LEO meteorological satellite using domestic technology in accordance with the “2020 master plan for space development promotion”. You have been given the job of program manager for this next generation meteorological satellite mission to provide data for numerical weather prediction. This mission aims to reduce 24-hour forecasting errors by about 10% in the Korean peninsula, but also to
contribute to global forecast error reduction. You are told to meet a total budget of 700 billion won and 5 years of operation. Operations will be conducted from two existing ground stations in the Korean Aerospace Research Institute, Daejeon, and the National Meteorological Satellite
Center, Jincheon. The Soyuz-2 launch vehicle will place the satellite into 850 km polar orbit in a north to south path. Launches are limited to 2500 kg in mass with dimensions of 1.5 x 1.5 x 1.5 there will be 2 launch opportunities available beginning in 2023. To satisfy the mission sponsors,the mission must be operational within 5 years.
1. Space
Mission Design
a. Define the
mission requirements and constraints
b. Derive the
system requirements and constraints
2. [40 points]
Remote-sensing Payloads
You and a
payload manager choose two sensors; Visible Infrared Imaging Radiometer Suite
(VIIRS) and
GNSS Radio Occultation (GNSS RO) receiver. VIIRS takes visible and infrared
observations of
atmosphere parameters at high temporal resolution. GNSS RO allows for a
vertical
scanning of successive layers of the atmosphere.
a. The VIIRS
instrument can collect data in 22 different spectral bands of the
electromagnetic
spectrum in the wavelengths between 0.41 μm to 12.01 μm.
i. Determine
the temperature range of objects which this sensor can detect.
ii. Convert the
wavelength range (0.41 μm to 12.01 μm) to frequency range.
b. VIIRS has a
swath with of 3060 km at the satellite’s average altitude of 850 km. This
swath width is
able to provide complete coverage of Earth across the day. The VIIRS
imaging optics
have a detector radius of 0.49 m and a sensor resolution of 4.45 m.
i. Find ground
radius
ii. Find sensor
focal length
iii. Find the
minimum sensor aperture
iv. Find the
sensor field of view
c. The GNSS RO
receiver can acquire GPS L1 and L2 signals
i. What are the
frequencies of GPS L1 and L2?
ii. What are
the error sources you need to remove from GPS signals in order to
obtain
atmospheric parameters from GPS RO sensors?
3. Space
Environment and Spacecraft
a. Do you think
your meteorological satellite (which you are working on) has potential
hazards from
micrometeoroids and space junk? If yes, describes what the hazards are. If
no, explain why
that is.
b. What are the
major problems in the vacuum environment of space? What would you ask
your ground
test engineer to do before you launch your satellite to space?
c. What are the
Van Allen radiation belts and what do they contain? Would you consider its
effects for
your mission design? Explain why?
4. Attitude
Control
You are going
to hire a new engineer who will develop the attitude control system for your
meteorological
satellite project. You will ask the following questions to a candidate. What
are
correct answers
you expect to hear from the candidate? Assume that you provide necessary
information to
him/her.
a. What is the
difference between attitude accuracy, slew, and slew rate?
b. What are
disturbance torques and how do they affect a spacecraft? Which ones do you
worry about
most for this satellite project?
c. What is the
force of air drag on a spacecraft with a cross-sectional area of 10 m2
in a
polar orbit at
850 km? Assume the air density is 2.53 x 10-10 km/m3 and CD = 1.0.
d. For the
meteorological satellite to provide accurate atmospheric parameters, the center
of
the sensor’s
FOV must not deviate from nadir by more than ?15 km.
i. Determine
the corresponding attitude accuracy required.
ii. Given this
accuracy, complete a conceptual design of the meteorological satellite
attitude
control subsystem. Remember that you need to meet the accuracy
requirement.
iii. Draw a
simple block diagram for your resulting subsystem.
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