PADRE Mission
Juan Carlos Martínez Oliveros on behalf of PADRE Team
The solar PolArization and Directivity X-Ray Experiment (PADRE) is a Sun spinner 12U cubesat observatory to detect solar flare X-rays from LEO.
PADRE was proposed to the Heliophysics Flight Opportunities for Research and Technology (NNH20ZDA001N-HFORT) program and selected in 2021.
PADRE is a collaboration between SSL/UCB, NASA-GSFC, SWRI, CEA-Saclay
PADRE has one science objective: determine the angular distribution of accelerated electrons from standalone and joint SolO/STIX observations.
PADRE will investigate the accelerated electron angular distribution in solar flares with two complementary approaches:
In other words, with PADRE we want to understand the acceleration and transport process(es) that occur in solar eruptive events or solar flares.
The science questions we want to answer are:
a) “How is magnetic energy previously stored in the solar corona converted into kinetic energy of charged particles during a solar flare?",
b) “What is the anisotropy of the hard X-ray-producing accelerated electrons?"
Electron beams penetrating the Electron beams penetrating the chromosphere are expected to produce anisotropic emission. Solar Orbiter and PADRE will observe emission from the same flare from different viewing angles with the same detectors.
A 1 year mission lifetime guarantees that flares will be observed by SO/STIX and PADRE/XDSOX with large angular separations regardless of launch date.
PADRE’s consist of two scientific instruments consists both optimized to study the directivity of solar X-ray emission, but using two different and complementary techniques, one base of polarization measurements and a second based in stereoscopic observations.
The X-ray Directivity with SO Experiment (XDSOX) is a straightforward instrument concept and makes use of existing SO/STIX flight-spare detectors provided by CEA-Saclay. Unlike STIX, XDSOX does not have grids and does not image HXRs as it is not necessary for the proposed science.
The Solar HARd x-ray Polarimeter (SHARP) consists of a cylindrical beryllium scatterer, surrounded by ~1 mm-thick CdTe photon counting detectors instrumented by Timepix2 ASICs.
12/1/2021
Formulation Phase
June 2022
System Requirements Review
Q2 2023
Design Review
Q4 2024
Environmental testing and Flight Readiness Review
Q2 2025
LAUNCH!!
PADRE Timeline
The launch of PADRE is well matched to the peak of solar cycle 25 and to the observation time of SO/STIX ensuring that many large flares will be observed by SHARP, and both SO/STIX and XDSOX at the same time.
XDSOX
SHARP
S-band
UHF-band
Communications
8
XDSOX
SHARP
S-band
UHF-band
PADRE will use an custom design UHF radio receiver design for the CURIE mission for commanding. The RF input of this receiver will be connected to a 3-dB power splitter and two 916MHz patch antennas.
For housekeeping and science telemetry downlink, the spacecraft will be equipped with an Emhiser 1 W S-band transmitter, another 3-dB power splitter and two circular polarized patch antennae
Science Objectives | | Measurement Requirements | Functional Requirements | Projected Performance | Mission Requirements (Top Level) |
What is the angular distribution of accelerated electron in solar flares? | SHARP | Determine HXR degree of linear polarization from LEO between 10 and ~90 keV | Low energy threshold of 20 keV | Low energy threshold of 3 keV | Sun Pointing |
High energy threshold of > 50 keV | High energy threshold of > 100 keV | Spinner, 15 rpm | |||
Energy resolution 10 keV | Energy resolution 2 keV | 1 year mission will ensure the routine spectropolarimetric observations of flares with significant degree of polarization to determine the angular distribution of flare accelerated electrons | |||
Photon time tagging to a precision no more than 5% of the spin period (~0.2 s) | Photon time tagging to better than 1 ms | ||||
Effective area 0.04 cm² (>20 keV): >20 flares per year with MDP(99%) of 5%. | Effective area 0.07 cm² (>20 keV): >40 flares per year with MDP(99%) of 5%. | ||||
XDSOX | Measure X-rays from flares from LEO between 10 and ~90 keV with Solar Orbiter | Low energy threshold of 10 keV | Low energy threshold of 3 keV | 1 year mission will ensure the co-observation of at least 4 flares with significant anisotropy and 8 flares with little to no expected anisotropy for cross-calibration | |
High energy threshold of > 90 keV | High energy threshold of 150 keV | ||||
Energy resolution 2 keV | Energy resolution ~1 keV FWHM | ||||
Determine the anisotropy to at least 15% between 30 and 60 keV | Spectral time resolution of 60s | Downlinking each flare photon with 1 ms time resolution | |||
| Effective area 0.05 cm² (10 to 15 keV); 2 cm² (30 to ~90 keV) | Effective area 0.2 cm² (10 to 15 keV); >2.5 cm² (30 to ~90 keV) |