Adaptive Secondary Mirror development for the UH-88 telescope

International audienceTNO and industrial partners VDL ETG, L3Harris and Hyperion are developing a novel Adaptive Secondary Mirror (ASM) for Ground Layer Adaptive Optics (GLAO) at the University of Hawaii's 88-inch telescope on Mauna Kea. The ASM is based on a unique actuator principle which delivers a >30µm PV 99% linear stroke at a very high efficiency in terms of force per unit of volume and of power. The adaptive mirror does not require active cooling and due to its compactness can be fitted within the same volume of the original passive mirror. The overall dimensions of the ASM for the UH88 are ø63cm with 204 actuators in a circular grid and an overall height of 13cm. The ULE mirror shell has an aspherical convex shape with a 4,2-meter radius of curvature and a thickness of 3,5mm. At the time of writing of this paper the project is in the critical design phase with installation on the telescope anticipated late 2020

Compact Hyperspectrals

Numerous Hyperspectral Imagers have been launched or are being built for resource management, monitoring anthropogenic effects on the troposphere gases, and for defense applications. Payloads such as Hyperion, EnMAP, HyspIRI, and SCHYAMACHY are instruments with mass in excess of 100 Kg. Technologies recently developed in precision manufacturing of aspherical mirrors, detectors, and spectral filters allow to shrink a hyperspectral instrument in an envelope that will fit on a small satellite, or even in a CubeSat. The reduction of mass, volume, and power is not the only problems to be solved to successfully use a hyperspectral on board of a small satellite. The amount of data acquired over one orbit can be as high as 1 TB (terabyte). To store and download the data can be unmanageable tasks for the resources of a small satellite. The reduced mass and volume of a compact hyperspectral comes at the expenses of a decreased signal to noise ratio. Can digital image processing and the knowledge acquired with the hyperspectral already in orbit help to compress the data to a manageable size? What type of information can be extracted from a compact hyperspectral? The paper describes the results obtained with the PhytoMapper, a technology demonstrator of a Compact Hyperspectral Instrument recently developed. The instrument fits in a volume of approximately 15 cm^3 (6 cubic inches) and has a mass of approximately 2 Kg. The instrument has a spectral resolution of 10nm, a field of view 34 degrees, and 2400 spectral bands. If flown on a 600km polar orbit, it will provide 100m spatial resolution and 3 days revisit time. The work presents the performance measured in the lab and the analyses performed to assess what type of mission objectives are achievable with this instrument. Further work has been done to push the envelope of a Hyperspectral within a CubeSat. A micro-telescope with a very aggressive optical design has been built and tested. The paper gives an overview of the performance that can be achieved with this extreme downscaled hyperspectral instrument and what, in the view of the Authors, can be the possible applications. A roadmap from the current technology status to the in-flight demonstration is finally presented

The Apertif Radio Transient System (ARTS): Design, commissioning, data release, and detection of the first five fast radio bursts

Fast radio bursts (FRBs) must be powered by uniquely energetic emission mechanisms. This requirement has eliminated a number of possible source types, but several remain. Identifying the physical nature of FRB emitters arguably requires good localisation of more detections, as well as broad-band studies enabled by real-time alerting. In this paper, we present the Apertif Radio Transient System (ARTS), a supercomputing radio-telescope instrument that performs real-time FRB detection and localisation on the Westerbork Synthesis Radio Telescope (WSRT) interferometer. It reaches coherent-addition sensitivity over the entire field of the view of the primary-dish beam. After commissioning results verified that the system performed as planned, we initiated the Apertif FRB survey (ALERT). Over the first 5 weeks we observed at design sensitivity in 2019, we detected five new FRBs, and interferometrically localised each of them to 0.4–10 sq. arcmin. All detections are broad band, very narrow, of the order of 1 ms in duration, and unscattered. Dispersion measures are generally high. Only through the very high time and frequency resolution of ARTS are these hard-to-find FRBs detected, producing an unbiased view of the intrinsic population properties. Most localisation regions are small enough to rule out the presence of associated persistent radio sources. Three FRBs cut through the halos of M31 and M33. We demonstrate that Apertif can localise one-off FRBs with an accuracy that maps magneto-ionic material along well-defined lines of sight. The rate of one every ~7 days ensures a considerable number of new sources are detected for such a study. The combination of the detection rate and localisation accuracy exemplified by the first five ARTS FRBs thus marks a new phase in which a growing number of bursts can be used to probe our Universe