Pascal Hallibert

MTG Flexible Combined Imager optical design and performances

Meteosat Third Generation is the next ESA Program of Earth Observation dedicated to Nowcasting and very short term Weather Forecasting (NWC), medium/short range Global and Regional Numerical Weather Prediction (NWP), and Climate and Air Composition Monitoring. The satellites will be operating from the Geostationary orbit using a 3 axes stabilized platform. The main instrument is called the Flexible Combined Imager (FCI), currently under development by Thales Alenia Space France (TAS-F). This instrument will provide full images of the Earth every 10 minutes in 16 spectral channels between 0.44 and 13.3 μm, with a ground resolution from 0.5 km to 2 km. The FCI is composed of a TMA telescope developed by Kayser-Threde (KT), which includes a Scan mirror, and a calibration mechanism with an embedded black body dedicated to accurate in-flight IR radiometric calibration and a Metallic Neutral density for dedicated VNIR Sun calibration. The image produced by the telescope is split into several spectral groups by a spectral separation assembly (SSA) with dichroïc beamsplitters. The output beams are collimated to ease the instrument integration, and reach the cold optics (CO-I) which focalize the optical beams onto the detectors. The cold optics and IR detectors are accurately positioned inside a common cryostat to improve registration between spectral channels. Spectral filters are integrated on top of the detectors in order to achieve the required spectral selection. This article will describe the optical design and the main optical performances of the FCI: image quality, very high line-of-sight stability, and an efficient stray-light rejection thanks to the implementation of dedicated baffles and a stringent control of contamination. The FCI currently under development is expected to exhibit a significant improvement of performances with respect to Meteosat Second Generation satellites.

The flexible combined imager onboard MTG: from design to calibration

The Meteosat Third Generation (MTG) Programme is being realised through the well-established and successful cooperation between EUMETSAT and ESA. It will ensure the continuity with, and enhancement of, operational meteorological and climate data from Geostationary Orbit as currently provided by the Meteosat Second Generation (MSG) system. The industrial Prime Contractor for the Space segment is Thales Alenia Space (France) with a core team consortium including OHB-Bremen (Germany) and OHB-Munich (Germany. This contract includes the provision of six satellites, four Imaging satellites (MTG-I) and two Sounding satellites (MTG-S), which will ensure a total operational life of the MTG system in excess of 20 years. A clear technical baseline has been established for both MTG-I and MTG-S satellites, and confirmed through a rigorous Preliminary Design Review (PDR) process that was formally concluded during 2013. Dedicated reviews have been held for all the main elements including the core instruments (Flexible Combined Imager (FCI) and Infrared Sounder (IRS)), the Platform (which is largely common for the two satellites), the Lightning Imager (LI) and the MTG-I and MTG-S satellites as a whole. The satellites and instruments are at the moment in preparation for the Structural and Thermal Models (STM). The FCI is designed to provide images of the Earth every 10 to 2.5 minutes in 16 spectral channels between 0.44 and 13.3 μm, with a ground resolution ranging from 0.5 km to 2 km. The on-board calibration is based on the use of a Metallic Neutral Density (MND) filter for VIS/NIR channels and a blackbody for the IR channels. This paper introduces the overall FCI design and its calibration concept covering VIS/NIR and IR domains and it describes how the use of the MND makes it possible to accurately correct the medium and long term radiometric drifts of the IR3.8 μm channel.

Design and component test results of the LSST Camera L1-L2 lens assembly

The Large Synoptic Survey Telescope (LSST) camera will be the largest camera ever constructed for astronomy. When light enters the camera it will first pass through the two large lenses of the L1-L2 Lens Assembly. This assembly consists of a 1.6 m spherical lens and a 1.2 m aspheric lens held in critical alignment by a carbon fiber composite structure. The structure is mounted to the camera structure by six adjustable struts, which provide the mechanism to align the L1-L2 Assembly to the rest of the camera optical system. Final optical performance of this assembly is based upon lens figure, lens alignment, and alignment stability. With manufacture of the individual components of the L1-L2 Lens assembly and testing of the integrated composite structure nearing completion, design, design drivers, and test results will be presented.

Instantaneous phase mapping deflectometry for dynamic deformable mirror characterization

We present an instantaneous phase mapping deflectometry (PMD) system in the context of measuring a continuous surface deformable mirror (DM). Deflectometry has a high dynamic range, enabling the full range of surfaces generated by the DM to be measured. The recent development of an instantaneous PMD system leverages the simple setup of the PMD system to measure dynamic objects with accuracy similar to an interferometer. To demonstrate the capabilities of this technology, we perform a linearity measurement of the actuator motion in a continuous surface DM, which is critical for closed loop control in adaptive optics applications. We measure the entire set of actuators across the DM as they traverse their full range of motion with a Shack-Hartman wavefront sensor, thereby obtaining the influence function. Given the influence function of each actuator, the DM can produce specific Zernike terms on its surface. We then measure the linearity of the Zernike modes available in the DM software using the instantaneous PMD system. By obtaining the relationship between modes, we can more accurately generate surface profiles composed of Zernike terms. This ability is useful for other dynamic freeform metrology applications that utilize the DM as a null component.

Imaging and spectral performance of the New Horizons Ralph instrument during the 2015 Pluto encounter (Conference Presentation)

The Ralph instrument on the New Horizons mission consists of a telescope that feeds two focal planes: the Multi-spectral Visible Imaging Camera (MVIC), a visible, near-IR imager and the Linear Etalon Imaging Spectral Array (LEISA), a short-wavelength IR spectral imager. During the encounter with the Pluto system in 2015, Ralph operated as expected collecting numerous high spatial resolution images of the main components of the system, Pluto and Charon, as well as the four much smaller objects Hydra, Kerberos, Nix and Styx. New Horizons, launched on January 19, 2006, is the first mission to explore Kuiper Belt Objects (KBOs).

The Large Synoptic Survey Telescope (Conference Presentation)

The Large Synoptic Survey Telescope (LSST) is a large aperture, wide-field, ground-based telescope designed to provide a time domain survey of the entire southern hemisphere in six optical bands. Over the ten-year duration of the survey, LSST will obtain ~800-1,000 images of every part of the southern sky, yielding a catalog of stars, galaxies, and moving small bodies in the solar system with nearly 40 billion objects. A diverse array of scientific investigations can be performed with a common database addressing topics ranging from the detection of potentially hazardous asteroids to the structure and evolution of the Universe as a whole. LSST incorporates an 8-m class primary mirror with a 3.2 billion pixel camera. I will discuss the design of this facility and our technical progress with construction and fabrication of the key components.

Development of the camera lens system for total solar eclipse observation (Conference Presentation)

Korea Astronomy and Space Science Institute (KASI) has been developing the Camera Lens System (CLS) for the Total Solar Eclipse (TSE) observation. In 2016 we have assembled a simple camera system including a camera lens, a polarizer, bandpass filters, and CCD to observe the solar corona during the Total Solar Eclipse in Indonesia. Even we could not obtain the satisfactory result in the observation due to poor environment, we obtained some lessons such as poor image quality due to ghost effect from the lens system. For 2017 TSE observation, we have studied and adapted the compact coronagraph design proposed by NASA. The compact coronagraph design dramatically reduces the volume and weight and can be used for TSE observation without an external occulter which blocks the solar disk. We are in developing another camera system using the compact coronagraph design to test and verify key components including bandpass filter, polarizer, and CCD, and it will be used for the Total Solar Eclipse (TSE) in 2017. We plan to adapt this design for a coronagraph mission in the future. In this report we introduce the progress and current status of the project and focus on optical engineering works including designing, analyzing, testing, and building for the TSE observation.

NEO deflection by laser ablation: experimental results (Conference Presentation)

Asteroids impact Earth daily. Some, like the Chelyabinsk Meteor that exploded over Siberia in 2013, can cause massive disruption to human enterprise (~

Developments in active optics for space instruments: an ESA perspective

33M in damages) and thousands of injuries. To mitigate this potentially disastrous threat, our group has posited a phased laser array which would be used to direct energy towards approaching asteroids or other dangerous near Earth objects (NEOs). The laser array would ablate the NEO’s surface, inducing mass ejection, that would then cause a reactant thrust on the NEO in the opposite direction of the laser. To verify this concept in a laboratory environment, this work quantitatively measured the thrust induced on basalt and other asteroid regolith simulant by a 350W laser array. By placing the sample target on a torsion balance and measuring its angle of deflection under ablation, it is possible to calculate the induced thrust per unit watt. This angular change is measured with a secondary laser that reflects off of the torsion balance into an optical position sensor. By comparing this paper’s experimental results with prior theoretical and computational work, we can surmise a theoretical relationship between NEO size and required laser power for future NEO deflection missions.

Meteosat Third Generation: The Infrared Sounder Instrument

An increasing need for higher resolution for both Science and Earth Observation applications demands a bigger entrance aperture of future optical payloads, leading to large primary mirrors, either monolithic or deployable. Correcting issues linked to manufacturing, integration, launch and use of large light-weighted optics (and associated structures), Active Optics constitutes an enabling technology for future large space instruments. This paper presents the current status of technological developments at ESA in this very promising field.