First observations from the SPICE EUV spectrometer on Solar Orbiter

¹ RAL Space, UKRI STFC Rutherford Appleton Laboratory, Didcot, UK
e-mail: andrzej.fludra@stfc.ac.uk
² Université Paris-Saclay, CNRS, Institut d’Astrophysique Spatiale, 91405 Orsay, France
³ Institute of Theoretical Astrophysics, University of Oslo, Oslo, Norway
⁴ Southwest Research Institute, Boulder, CO, USA
⁵ Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany
⁶ Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center, Davos Dorf, Switzerland
⁷ NASA Goddard Space Flight Center, Greenbelt, MD, USA
⁸ European Space Agency, ESTEC, Noordwijk, The Netherlands
⁹ ADNET Systems Inc., NASA Goddard Space Flight Center, Greenbelt, MD, USA
¹⁰ European Space Agency, ESAC, Villanueva de la Cañada, Spain
¹¹ ETH Zürich, IPA, HIT building, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
¹² School of Space Research, Kyung Hee University, Yongin, Gyeonggi-Do 446-701, Republic of Korea
¹³ Northumbria University, Newcastle upon Tyne NE1 8ST, UK

Received: 30 April 2021
Accepted: 6 September 2021

Abstract

Aims. We present first science observations taken during the commissioning activities of the Spectral Imaging of the Coronal Environment (SPICE) instrument on the ESA/NASA Solar Orbiter mission. SPICE is a high-resolution imaging spectrometer operating at extreme ultraviolet (EUV) wavelengths. In this paper we illustrate the possible types of observations to give prospective users a better understanding of the science capabilities of SPICE.

Methods. We have reviewed the data obtained by SPICE between April and June 2020 and selected representative results obtained with different slits and a range of exposure times between 5 s and 180 s. Standard instrumental corrections have been applied to the raw data.

Results. The paper discusses the first observations of the Sun on different targets and presents an example of the full spectra from the quiet Sun, identifying over 40 spectral lines from neutral hydrogen and ions of carbon, oxygen, nitrogen, neon, sulphur, magnesium, and iron. These lines cover the temperature range between 20 000 K and 1 million K (10 MK in flares), providing slices of the Sun’s atmosphere in narrow temperature intervals. We provide a list of count rates for the 23 brightest spectral lines. We show examples of raster images of the quiet Sun in several strong transition region lines, where we have found unusually bright, compact structures in the quiet Sun network, with extreme intensities up to 25 times greater than the average intensity across the image. The lifetimes of these structures can exceed 2.5 hours. We identify them as a transition region signature of coronal bright points and compare their areas and intensity enhancements. We also show the first above-limb measurements with SPICE above the polar limb in C III, O VI, and Ne VIII lines, and far off limb measurements in the equatorial plane in Mg IX, Ne VIII, and O VI lines. We discuss the potential to use abundance diagnostics methods to study the variability of the elemental composition that can be compared with in situ measurements to help confirm the magnetic connection between the spacecraft location and the Sun’s surface, and locate the sources of the solar wind.

Conclusions. The SPICE instrument successfully performs measurements of EUV spectra and raster images that will make vital contributions to the scientific success of the Solar Orbiter mission.