The mid-infrared instrument for the James Webb space telescope, II: design and build

Instrumentatio

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Design of a micromanipulation system for high temperature operation in an Environmental Scanning Electron Microscope (ESEM)

The Environmental Scanning Electron Microscope (ESEM) allows the sample to be imaged under a low pressure atmosphere. The ability to micromanipulate with precision within heated power systems in an ESEM will enable a greater understanding of the behaviour of materials at high temperature. Heating stages for ESEM’s are commercially available but none include micromanipulation systems. Creating such a system is fraught with design problems. This is because the piezoelectric transducers, required to generate the precise range of movement within the heated environment, are unable to operate at temperatures exceeding about 90°C and require thermal protection. Here we have used a one dimensional probe as a model of a three dimensional manipulator. We have introduced a thermal break and a thermally insulating extension arm to protect the piezoelectric from heat. We have applied finite element analysis to test the design concepts before practical implementation. This ensures that the piezoelectric transducers in the costly practical devices are not placed at risk. The predictions have been validated with subsequent experimental work although there are some discrepancies to resolve. An example of the movement of aluminium alloy grains and copper powder particles using the one-dimensional manipulator are given

Elfen: A CubeSat mission to measure heavy ions on both the dayside and nightside of Earth's magnetosphere

International audienceThe Elfen mission has two science goals: (1) To understand the heavy ion composition of the solar wind and its influence on the dayside of the Earth’s magnetosphere, (2) To understand the origin of and processing involving ions in the plasma sheet. We propose a mission using two instruments; a mass spectrometer to determine the in situ heavy ion composition, and a magnetometer to help determine the contemporaneous plasma regime of the Earth’s magnetosphere traversed by the spacecraft.The influence of solar wind heavy ions, such as C6+, or O7+ in the solar-terrestrial system is poorly understood, and no dedicated mission to understand these ions has been undertaken. It is unknown, for example, if charged iron atoms in the magnetosphere are of ionospheric or solar wind origin, and of their influence on the mesosphere. Recently analysis from Cluster has suggested that both the inflow and outflow contribute to ions in the magnetosphere. Ion spatial segregation, particularly in areas such as the magnetospheric cusps, has unknown influence on magnetosphere-ionosphere coupling. In addition, temporal changes in solar wind composition will lead to changes in the total X-ray emission via charge exchange that can occur on impact of an ion with the neutral hydrogen exosphere. This has implications for current and future X-ray imaging missions, such as the joint ESA and Chinese Academy of Sciences SMILE mission, or for NASA’s LEXI mission. Heavy ion processes in the plasma sheet have only been sampled by an extremely limited number of previous missions. The origin of the plasma sheet is hotly debated. Diffusion may occur through the flanks of the magnetosheath, e.g. through the Kelvin Helmholtz instability, or ions may be injected via nightside reconnection in the tail. Alternatively, plasma may be injected sporadically under certain magnetospheric conditions.Elfen, in its current configuration as a ~16U CubeSat, from its 12 RE circular orbit, will make composition measurements at 10 second cadence on the nightside, and at a minimum of 1 minute on the dayside. The magnetometer will have sensitivity of 2 nT at a cadence of 10 Hz. The Elfen team comprises partners from the UK, US, France, and Norway. We will present a recent Concurrent Design Facility study that has significantly matured the initial science concept. See: https://elfen.le.ac.uk

Elfen: A CubeSat mission to measure heavy ions on both the dayside and nightside of Earth's magnetosphere

International audienceThe Elfen mission has two science goals: (1) To understand the heavy ion composition of the solar wind and its influence on the dayside of the Earth’s magnetosphere, (2) To understand the origin of and processing involving ions in the plasma sheet. We propose a mission using two instruments; a mass spectrometer to determine the in situ heavy ion composition, and a magnetometer to help determine the contemporaneous plasma regime of the Earth’s magnetosphere traversed by the spacecraft.The influence of solar wind heavy ions, such as C6+, or O7+ in the solar-terrestrial system is poorly understood, and no dedicated mission to understand these ions has been undertaken. It is unknown, for example, if charged iron atoms in the magnetosphere are of ionospheric or solar wind origin, and of their influence on the mesosphere. Recently analysis from Cluster has suggested that both the inflow and outflow contribute to ions in the magnetosphere. Ion spatial segregation, particularly in areas such as the magnetospheric cusps, has unknown influence on magnetosphere-ionosphere coupling. In addition, temporal changes in solar wind composition will lead to changes in the total X-ray emission via charge exchange that can occur on impact of an ion with the neutral hydrogen exosphere. This has implications for current and future X-ray imaging missions, such as the joint ESA and Chinese Academy of Sciences SMILE mission, or for NASA’s LEXI mission. Heavy ion processes in the plasma sheet have only been sampled by an extremely limited number of previous missions. The origin of the plasma sheet is hotly debated. Diffusion may occur through the flanks of the magnetosheath, e.g. through the Kelvin Helmholtz instability, or ions may be injected via nightside reconnection in the tail. Alternatively, plasma may be injected sporadically under certain magnetospheric conditions.Elfen, in its current configuration as a ~16U CubeSat, from its 12 RE circular orbit, will make composition measurements at 10 second cadence on the nightside, and at a minimum of 1 minute on the dayside. The magnetometer will have sensitivity of 2 nT at a cadence of 10 Hz. The Elfen team comprises partners from the UK, US, France, and Norway. We will present a recent Concurrent Design Facility study that has significantly matured the initial science concept. See: https://elfen.le.ac.uk

European Radioisotope Thermoelectric Generators (RTGs) and Radioisotope Heater Units (RHUs) for Space Science and Exploration

Radioisotope power systems utilising americium-241 as a source of heat have been under development in Europe as part of a European Space Agency funded programme since 2009. The aim is to develop all of the building blocks that would enable Europe to launch and operate deep space and planetary missions in environments where use of solar power or alternative power generation technologies is challenging. Although some technical and policy work activity predate the ESA programme, the maturity of the technology has now reached a level that it can be incorporated in mission studies and roadmaps targeting the period from the mid 2020s onwards. This paper describes the state of the art in European radioisotope thermoelectric generators and radioisotope heater units. This paper includes: the evolution of the technical programme in detail; descriptions of the design; evolution of RTG and RHU devices from laboratory prototypes to more advanced fully functional systems; and experimental data obtained to date. This paper also outlines the technical challenges and multidisciplinary skills required to develop what is a world leading, original, significant and transformative technology solution for planetary science and exploration missions from the mid 2020s onwards.JRC.G.I.3-Nuclear Fuel Safet