Description

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.