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
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
iii. Draw a simple block diagram for your resulting subsystem.