Detection of Coronal Mass Ejections at L1 and Forecast of Their Geoeffectiveness

A novel tool aimed to detect solar coronal mass ejections (CMEs) at the Lagrangian point L1 and to forecast their geoeffectiveness is presented in this paper. This approach is based on the analysis of in situ magnetic field and plasma measurements to compute some important magnetohydrodynamic quantities of the solar wind (the total pressure, the magnetic helicity, and the magnetic and kinetic energy), which are used to identify the CME events, that is their arrival and transit times, and to assess their likelihood for impacting the Earths magnetosphere. The method is essentially based on the comparison of the topological properties of the CME magnetic field configuration and of the CME energetic budget with those of the quasi-steady ambient solar wind. The algorithm performances are estimated by testing the tool on solar wind data collected in situ by the Wind spacecraft from 2005 to 2016. In the scanned 12 yr time interval, it results that (i) the procedure efficiency is of 86% for the weakest magnetospheric disturbances, increasing with the level of the geomagnetic storming, up to 100% for the most intense geomagnetic events, (ii) zero false positive predictions are produced by the algorithm, and (iii) the mean delay between the potentially geoeffective CME detection and the geomagnetic storm onset if of 4 hr, with a 98% 2-8 hr confidence interval. Hence, this new technique appears to be very promising in forecasting space weather phenomena associated to CMEs

Laboratory testbed for the calibration and the validation of the shadow position sensor subsystem of the PROBA3 ESA mission

n/

A virtual appliance as proxy pipeline for the Solar Orbiter/Metis coronagraph

Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted to the study of the Sun that will be launched in October 2018. Metis is designed to perform imaging of the solar corona in the UV at 121.6 nm and in the visible range where it will accomplish polarimetry studies thanks to a variable retarder plate. Due to mission constraints, the telemetry downlink on the spacecraft will be limited and data will be downloaded with delays that could reach, in the worst case, several months. In order to have a quick overview on the ongoing operations and to check the safety of the 10 instruments on board, a high-priority downlink channel has been foreseen to download a restricted amount of data. These so-called Low Latency Data will be downloaded daily and, since they could trigger possible actions, they have to be quickly processed on ground as soon as they are delivered. To do so, a proper processing pipeline has to be developed by each instrument. This tool will then be integrated in a single system at the ESA Science Operation Center that will receive the downloaded data by the Mission Operation Center. This paper will provide a brief overview of the on board processing and data produced by Metis and it will describe the proxy-pipeline currently under development to deal with the Metis low-latency data

The shadow position sensors (SPS) formation flying metrology subsystem for the ESA PROBA-3 mission: present status and future developments

PROBA-3 [1] [2] is a Mission of the European Space Agency (ESA) composed of two formation-flying satellites, planned for their joint launch by the end of 2018. Its main purposes have a dual nature: scientific and technological. In particular, it is designed to observe and study the inner part of the visible solar corona, thanks to a dedicated coronagraph called ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), and to demonstrate the in-orbit formation flying (FF) and attitude control capability of its two satellites. The Coronagraph payload on-board PROBA-3 consists of the following parts: the Coronagraph Instrument (CI) with the Shadow Position Sensor (SPS) on the Coronagraph Spacecraft (CSC), the Occulter Position Sensor (OPSE) [3] [4] and the External Occulting (EO) disk on the Occulter Spacecraft (OSC). The SPS subsystem [5] is one of the main metrological devices of the Mission, adopted to control and to maintain the relative (i.e. between the two satellites) and absolute (i.e. with respect to the Sun) FF attitude. It is composed of eight micro arrays of silicon photomultipliers (SiPMs) [6] that shall be able to measure, with the required sensitivity and dynamic range as asked by ESA, the penumbral light intensity on the Coronagraph entrance pupil. With the present paper we describe the testing activities on the SPS breadboard (BB) and Development Model (DM) as well as the present status and future developments of this PROBA-3 metrological subsystem

PROBA-3 mission and the Shadow Position Sensors: Metrology measurement concept and budget

PROBA-3 is a space mission of the European Space Agency that will test, and validate metrology and control systems for autonomous formation flying of two independent satellites. PROBA-3 will operate in a High Elliptic Orbit and when approaching the apogee at 6·104 Km, the two spacecraft will align to realize a giant externally occulted coronagraph named ASPIICS, with the telescope on one satellite and the external occulter on the other one, at inter-satellite distance of 144.3 m. The formation will be maintained over 6 hrs across the apogee transit and during this time different validation operations will be performed to confirm the effectiveness of the formation flying metrology concept, the metrology control systems and algorithms, and the spacecraft manoeuvring. The observation of the Sun's Corona in the field of view [1.08;3.0]RSun will represent the scientific tool to confirm the formation flying alignment. In this paper, we review the mission concept and we describe the Shadow Position Sensors (SPS), one of the metrological systems designed to provide high accuracy (sub-millimetre level) absolute and relative alignment measurement of the formation flying. The metrology algorithm developed to convert the SPS measurements in lateral and longitudinal movement estimation is also described and the measurement budget summarized

Design status of ASPIICS, an externally occulted coronagraph for PROBA-3

The "sonic region" of the Sun corona remains extremely difficult to observe with spatial resolution and sensitivity sufficient to understand the fine scale phenomena that govern the quiescent solar corona, as well as phenomena that lead to coronal mass ejections (CMEs), which influence space weather. Improvement on this front requires eclipse-like conditions over long observation times. The space-borne coronagraphs flown so far provided a continuous coverage of the external parts of the corona but their over-occulting system did not permit to analyse the part of the white-light corona where the main coronal mass is concentrated. The proposed PROBA-3 Coronagraph System, also known as ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun), with its novel design, will be the first space coronagraph to cover the range of radial distances between ~1.08 and 3 solar radii where the magnetic field plays a crucial role in the coronal dynamics, thus providing continuous observational conditions very close to those during a total solar eclipse. PROBA-3 is first a mission devoted to the in-orbit demonstration of precise formation flying techniques and technologies for future European missions, which will fly ASPIICS as primary payload. The instrument is distributed over two satellites flying in formation (approx. 150m apart) to form a giant coronagraph capable of producing a nearly perfect eclipse allowing observing the sun corona closer to the rim than ever before. The coronagraph instrument is developed by a large European consortium including about 20 partners from 7 countries under the auspices of the European Space Agency. This paper is reviewing the recent improvements and design updates of the ASPIICS instrument as it is stepping into the detailed design phase

Polarimetric calibrations and astronomical polarimetry in the V-band with Solar Orbiter/METIS instrument

METIS is one of the remote sensing instruments on board the ESA- Solar Orbiter mission, that will be launched in July 2017. The Visible Light Channel (VLC) of the instrument is composed by an achromatic LC-based polarimeter for the study of the linearly polarized solar K-corona in the 580-640 nm bandpass. The laboratory calibrations with spectropolarimetric techniques and the in-flight calibrations of this channel, using some well knows linearly polarized stars in the FoV of the instrument with a degree of linear polarization DOLP > 10% are here discussed. The selection of the stars and the use of other astronomical targets (i.e. planets, comets,\u2026) and the opportunity of measurements of the degree of linear polarization in the visible bandpass of some astronomical objects (i.e. Earth, comets,\u2026) are also objects of this paper

OPSys: optical payload systems facility for space instrumentation integration and calibration

The Optical Payload System (OPSys) is an INAF (italian National Institute for Astrophysics) facility hosted by Aerospace Logistics Technology Engineering Company (ALTEC SpA) in Turin, Italy. The facility is composed by three clean rooms having different cleanliness levels, a thermo-vacuum chamber (SPOCC, Space Optics calibration Chamber) with a motorized optical bench and several light sources covering the range from the extreme ultraviolet to the red light wavelengths. The SPOCC has been designed having in mind the very stringent requirements of the calibration of solar coronagraphs and the suppression of the stray-light. The facility and the optical performances will be described here. The calibration campaign performed on Metis space coronagraph will be reported as a case study

Wide field of view liquid crystals-based modulator for the polarimeter of the Metis/Solar Orbiter

Metis is an inverted occulted coronagraph on-board the ESA/Solar Orbiter mission. The visible light path of the instrument will observe the "white" light (580-640 nm) linearly-polarized emission from the solar corona. The coronal polarized brightness allows retrieval of physical parameters such as the electron density and temperature of the K-corona. The Metis polarimeter comprises a quarter-wave retarder, the liquid crystal polarization modulation package (PMP) and a linear polarizer working as polarization analyser. The PMP consists of two Anti-Parallel Nematic Liquid Crystal Variable Retarders (LCVRs) with the fast axes parallels one to each other and a pre-tilted angle of the molecules in opposite direction, in order to maximize the homogeneity of the retardance across instrumental wide field of view: 7 deg. This presentation reports the characterization of the PMP breadboard (BB), fully representative of the optical/polarimetric performances of the ight model. This characterization consisted in determining the performances of the device in terms of retardance as function of the applied voltage at different temperatures, angle of incidence and the variation of the retardance as a function of the wavelength. The calibrations were performed by measuring the complete Mueller matrix of the PMP-BB. The experimental results have been compared with the parameters of the theoretical model (e.g., depolarization, effective retardance, cells misalignment)

On-board CME detection algorithm for the Solar Orbiter-METIS coronagraph

The METIS coronagraph is one of the instruments part of the payload of the ESA - Solar Orbiter mission to be launched in 2017. The spacecraft will operate much like a planetary encounter mission, with the main scientific activity taking place with the remote-sensing instruments during three 10-days intervals per orbit: optimization of the different instrument observing modes will be crucial. One of the key scientific targets of METIS will be the study of transient ejections of mass through the solar corona (Coronal Mass Ejections - CMEs) and their heliospheric evolution. METIS will provide for the first time imaging of CMEs in two different wavelengths: VL (visible light 580- 640 nm) and UV (Lyman-α line of HI at 121.6 nm). The detection of transient phenomena shall be managed directly by the METIS Processing and Power Unit (MPPU) by means of both external triggers ("flags") coming from other Solar Orbiter instruments, and internal "flags" produced directly by the METIS on-board software. METIS on-board algorithm for the automatic detection of CMEs will be based on running differences between consecutive images re-binned to very low resolution and thresholded for significant changes over a minimum value. Given the small relative variation of white light intensity during CMEs, the algorithm will take advantage of VL images acquired with different polarization angles to maximize the detection capability: possible false detections should be automatically managed by the algorithm. The algorithm will be able to provide the CME first detection time, latitudinal direction of propagation on the plane of the sky (within 45 degrees), a binary flag indicating whether a "halo CME" has been detected