by J. Biggs and C. Tang, Maidenhead, England,
Open University Press, 2007, 360 pp., £29.99, ISBN-13: 978-0-335-22126-4

Teaching for quality learning at university

This chapter will discuss several kinds of sensors and actuators used to determine and control spacecraft attitude [26, 44, 54, 66]. The history of attitude sensor development has emphasized increased resolution and accuracy as well as decreased size, weight, and power (often abbreviated as SWaP). Actuator technologies have also been scaled down to be appropriate for microsatellites and cubesats. We begin with a brief introduction to redundancy considerations, and then consider some specific sensors and actuators.

Sensors and Actuators

http://systemarchitect.mit.edu/docs/selva12b.pdf

A survey and assessment of the capabilities of Cubesats for Earth observation

The Geostationary Operational Environmental Satellite R-series (GOES-R) is the next block of four satellites to follow the existing GOES constellation currently operating over the Western Hemisphere. Advanced spacecraft and instrument technology will support expanded detection of environmental phenomena, resulting in more timely and accurate forecasts and warnings. Advancements over current GOES capabilities include a new capability for total lightning detection (cloud and cloud-to-ground flashes) from the Geostationary Lightning Mapper (GLM), and improved cloud and moisture imagery with the 16-channel Advanced Baseline Imager (ABI). The GLM will map total lightning activity continuously day and night with near-uniform storm-scale spatial resolution of 8 km with a product refresh rate of less than 20 s over the Americas and adjacent oceanic regions in the western hemisphere. This will aid in forecasting severe storms and tornado activity, and convective weather impacts on aviation safety and efficiency. In parallel with the instrument development, an Algorithm Working Group (AWG) Lightning Detection Science and Applications Team developed the Level 2 (stroke and flash) algorithms from the Level 1 lightning event (pixel level) data. Proxy data sets used to develop the GLM operational algorithms as well as cal/val performance monitoring tools were derived from the NASA Lightning Imaging Sensor (LIS) and Optical Transient Detector (OTD) instruments in low Earth orbit, and from ground-based lightning networks and intensive prelaunch field campaigns. The GLM will produce the same or similar lightning flash attributes provided by the LIS and OTD, and thus extend their combined climatology over the western hemisphere into the coming decades. Science and application development along with preoperational product demonstrations and evaluations at NWS forecast offices and NOAA testbeds will prepare the forecasters to use GLM as soon as possible after the planned launch and checkout of GOES-R in late 2015. New applications will use GLM alone, in combination with the ABI, or integrated (fused) with other available tools (weather radar and ground strike networks, nowcasting systems, mesoscale analysis, and numerical weather prediction models) in the hands of the forecaster responsible for issuing more timely and accurate forecasts and warnings.

The GOES-R Geostationary Lightning Mapper (GLM)

Blue jets, gigantic jets, cloud-to-cloud discharges and cloud-to-ground lightning are all electrical discharges from thunderclouds. An analysis of numerical simulations and observations of these phenomena places them all in a unifying framework. Thunderstorms occasionally produce upward discharges, called blue jets and gigantic jets, that propagate out of the storm top towards or up to the ionosphere1,2,3,4. Whereas the various types of intracloud and cloud-to-ground lightning are reasonably well understood, the cause and nature of upward discharges remains a mystery. Here, we present a combination of observational and modelling results that indicate two principal ways in which upward discharges can be produced. The modelling indicates that blue jets occur as a result of electrical breakdown between the upper storm charge and the screening charge attracted to the cloud top; they are predicted to occur 5–10 s or less after a cloud-to-ground or intracloud discharge produces a sudden charge imbalance in the storm. An observation is presented of an upward discharge that supports this basic mechanism. In contrast, we find that gigantic jets begin as a normal intracloud discharge between dominant mid-level charge and a screening-depleted upper-level charge, that continues to propagate out of the top of the storm. Observational support for this mechanism comes from similarity with ‘bolt-from-the-blue’ discharges5 and from data on the polarity of gigantic jets6. We conclude that upward discharges are analogous to cloud-to-ground lightning. Our explanation provides a unifying view of how lightning escapes from a thundercloud.

Upward Electrical Discharges From Thunderstorms

The Atmosphere-Space Interactions Monitor (ASIM) is an instrument suite on the International Space Station (ISS) for measurements of lightning, Transient Luminous Events (TLEs) and Terrestrial Gamma-ray Flashes (TGFs). Developed in the framework of the European Space Agency (ESA), it was launched April 2, 2018 on the SpaceX CRS-14 flight to the ISS. ASIM was mounted on an external platform of ESA’s Columbus module eleven days later and is planned to take measurements during minimum 3 years. The instruments are an x- and gamma-ray monitor measuring photons from 15 keV to 20 MeV, and an array of three photometers and two cameras measuring in bands at: 180–250 nm, 337 nm and 777.4 nm. Additional objectives that can be addressed with the instruments relate to space physics like aurorae and meteors, and to Earth observation such as dust- and aerosol effects on cloud electrification. The paper describes the scientific objectives of the ASIM mission, the instruments, the mission architecture and the international collaboration supported by the ASIM Science Data Centre. ASIM is the first space mission with a comprehensive suite of instruments designed to measure TLEs and TGFs. Two companion papers describe the instruments in more detail (Ostgaard et al. in Space Sci. Rev., 2019; Chanrion et al. in Space Sci. Rev., 2019).

/pdf/the-asim-mission-on-the-international-space-station-30a43our20.pdf

The ASIM Mission on the International Space Station

The Modular Multispectral Imaging Array (MMIA) is a suite of optical sensors mounted on an external platform of the European Space Agency’s Columbus Module on the International Space Station. The MMIA, together with the Modular X- and Gamma- ray Sensor (MXGS), are the two main instruments forming the Atmosphere-Space Interactions Monitor (ASIM). The primary scientific objectives of the ASIM mission are to study thunderstorm electrical activity such as lightning, Transient Luminous Emissions (TLEs) and Terrestrial Gamma-ray Flashes (TGFs) by observing the associated emissions in the UV, near-infrared, x- and gamma-ray spectral bands. The MMIA includes two cameras imaging in 337 nm and 777.4 nm, at up to 12 frames per second, and three high-speed photometers at 180–230 nm, 337 nm and 777.4 nm, sampling at rates up to 100 kHz. The paper describes the MMIA and the aspects that make it an essential tool for the study of thunderstorms. The mission architecture is described in Neubert et al. (Space Sci. Rev. 215:26, 2019, this issue) and the MXGS instruments in Ostgaard et al. (Space Sci. Rev. 215:23, 2019, this issue).

/pdf/the-modular-multispectral-imaging-array-mmia-of-the-asim-2qki45t966.pdf

The Modular Multispectral Imaging Array (MMIA) of the ASIM Payload on the International Space Station

The Atmosphere-Space Interactions Monitor (ASIM) is an instrument suite on the International Space Station (ISS) for measurements of lightning, Transient Luminous Events (TLEs) and Terrestrial Gamma-ray Flashes (TGFs). Developed in the framework of the European Space Agency (ESA), it was launched April 2, 2018 on the SpaceX CRS-14 flight to the ISS. ASIM was mounted on an external platform of ESA's Columbus module eleven days later and is planned to take measurements during minimum 3 years.

/pdf/the-asim-mission-on-the-international-space-station-5bjvpl6811.pdf

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/pdf/modeling-earth-albedo-for-satellites-in-earth-orbit-4t3h78tdou.pdf

Modeling Earth Albedo for Satellites in Earth Orbit

This thesis focuses on Earth albedo modeling when applying S un sensors in spacecraft attitude determination. Since the recent development of th e CubeSat pico-satellite concept, numerous universities have initiated student satell ite projects. The minimal size of the CubeSats limits the hardware configuration, which, fo r an attitude determination point-of-view, only allows simple attitude sensors with li mited accuracy. This motivates the development of advanced algorithms capable of improvin g the estimation results through enhanced models of the space environment. The main contribution of this thesis is the development of an E rth albedo model, based on measurements of the Earth reflectivity by the Total O zone Mapping Spectrometer instruments on-board NASA’s Earth Probe satellite. Th e Earth albedo model may be used to calculate the amount of Earth albedo on a satellite given a Sun, Earth, and spacecraft constellation. The model results are verified us ing telemetry data from the Danish Ørsted satellite. The secondary contribution of the thesis is an investigatio n in attitude determination algorithms, where the Earth albedo model is applied. A s ingle-point Q-Method algorithm, which uses magnetometer and Sun sensor data, is d erive . The Sun sensor data is Earth albedo corrected using the Earth albedo mod el. In order to improve the performance of the attitude determination, an Extended Kalman Filter is developed. The Extended Kalman Filter includes knowledge of the spacec r ft dynamics by applying non-linear models of the attitude propagation. The Exte nded Kalman Filter also enables attitude determination during eclipse, during whi ch Sun sensor measurements are invalid. Due to the highly non-linear behavior of the Sun se sor measurements, an Unscented Kalman Filter is developed, and the results are compared to those of the Extended Kalman Filter. Additionally the possibilty of non -li ear measurement description in the Unscented Kalman Filter enables three-axis atti tude determination from Sun sensors only. The Earth albedo modeling software is distributed as a S IMULINK toolbox for the MATLAB software from Mathworks. In addition to improving attitudetermination

/pdf/spacecraft-attitude-determination-with-earth-albedo-41oejyecti.pdf

Dan Bhanderi

Papers

The ASIM Mission on the International Space Station

The Modular Multispectral Imaging Array (MMIA) of the ASIM Payload on the International Space Station

The ASIM Mission on the International Space Station

Modeling Earth Albedo for Satellites in Earth Orbit

Spacecraft Attitude Determination with Earth Albedo Corrected Sun Sensor Measurements