(note that before March 2023, this SOOP was called CC_OFFPOI_OOF)

General description

This SOOP is designed to observe the corona while Parker Solar Probe (PSP) is in quadrature with Solar Orbiter during a PSP perihelion passage. An off-point to the limb is required, remote-sensing instruments aboard Solar Orbiter observe the source region of solar wind that will be later encountered by Parker Solar Probe.

Due to PSP moving very fast during its perihelion passages, observing the Sun exactly during the PSP quadrature with Solar Orbiter will not work – the solar wind plasma departing from the Sun at this moment will not arrive to PSP as PSP will move away. One therefore needs to estimate the moment of departure of plasma from the Sun. As the detailed solar wind acceleration profile at the required moment and in the coronal region of interest is not known, ballistic approximation with a constant average solar wind speed is adopted. Recent works by Telloni et al. (2021) and Biondo et al. (2022) indicate that speeds around 150 – 200 km/s may be appropriate. The value of 200 km/s is assumed.

Default SOOP duration: 3 hours

Pointing requirements: east or west limb (depending above which the Parker Solar Probe (PSP) passes)

Triggers: none

Observations requirement (baseline)

The execution of this SOOP starts with a 5-minute slew. The slew is followed by a limb pointing for 3 hours (the corresponding Flight-Dynamics event is called CALIB_OFFPOI_OOF).

The SOOP Kitchen also lists POINT_LIMB (direction: EAST or WEST). After the off-point, another 5-minute slew returns the spacecraft to the disk center pointing. The direction of the off-point should be known in advance if the SOOP is scheduled outside a remote-sensing window.

Science objectives

The goal of the SOOP is to acquire above-the-limb observations of the source region of the solar wind plasma that will be later sampled in situ by Parker Solar Probe. This goal is closely linked to the main science objective of Solar Orbiter, i.e. the science of connecting solar and heliospheric phenomena. Correlating solar wind properties measured in situ by Parker Solar Probe with the properties of the coronal plasma measured by remote-sensing instruments aboard Solar Orbiter can be well done during a quadrature, when Parker Solar Probe passes above a limb observed by Solar Orbiter. Off-pointing to a limb allows SPICE and EUI to acquire high-cadence observations of the solar wind source region, which can provide data on plasma densities, temperatures, composition, Doppler shifts, and small-scale coronal dynamics.

Instances run / planned

The details of the SOOP that was run in the past are available:

https://docs.google.com/spreadsheets/d/1woSXqnVh8u6Gmdm4zfvBEdIjy2265JfSfaMaSsm2OpA/edit - gid=614843885

(note that before March 2023, this SOOP was called CC_OFFPOI_OOF)

22 February 2022, 18:00 – 21:10 (SOOP coordinator: A. Zhukov)

• east limb
• EUI/FSI at 5-minute cadence in both passbands
• EUI/HRI at 30-minute cadence in both passbands
• SPICE raster lines: Mg IX (706 Å), Ne VIII (770 Å), Ne VIII (780 Å), C III (977 Å), Ly-beta (1025 Å), O VI (1032 Å), O VI (1037 Å)
• No data were taken by PHI due to issues after the flight software update.
• Metis VL pB images, 2 images at 1 hour cadence, 6 images at 15 min cadence
• SoloHI: 2 × 2 binning; four images with each of inner tiles (48 min cadence); two images with each of outer tiles (96 min cadence).

26 February 2022, 05:40 – 08:50  (SOOP coordinator: A. Zhukov)

• west limb
• no SoloHI
• EUI/FSI at 5-minute cadence in both passbands
• EUI/HRI at 30-minute cadence in both passbands
• SPICE raster lines: Mg IX (706 Å), Ne VIII (770 Å), Ne VIII (780 Å), S V (786 Å), C III (977 Å), Ly-beta (1025 Å), O VI (1032 Å), O VI (1037 Å)
• PHI/HRT with the limb pointing, 6 datasets. No FDT data before 28/02.
• Metis VL pB images, 6 images at 30 min cadence

11 December 2022, 04:00 – 07:10  (SOOP coordinator: A. Zhukov)

• west limb
• no SoloHI
• EUI/FSI at 3-minute cadence in both passbands
• EUI/HRI_EUV at 4.5-second cadence
• EUI/HRI_LYA at 30 s cadence

15 March 2023, 11:45 – 14:55 (SOOP coordinator: A. Zhukov)

• east limb
• EUI/FSI at 10-minute cadence in both passbands
• EUI/HRI_EUV at 60-second cadence

Planned: 

21 June 2023, 15:00 – 18:10 (SOOP coordinator: A. Zhukov)  

27 September 2023, 02:30 – 05:30 (at 0.36 au, with the Metis door closed).  (SOOP coordinator: A. Zhukov)

• east limb

Science outcomes

Lessons learned: according to the PHI team, synoptic observations with FDI only make sense with disk-center pointing.

According to the SoloHI team, an off-point makes F-corona removal almost impossible if one doesn't have a large sample of images to work with. Long-duration off-points with gradual pointing change are preferred. If shorter off-points are needed, then it would be better to run a higher cadence sequence focused on the inner tiles.

Original SOOP proposers

Bernd Inhester