Farside Radio Interferometer In-Situ

Manuel Martin Soriano – ASTE 527 – 13 December 2022

Farside Radio Interferometer In-Situ (FRIIS)

• Strategic utilization of the RF silent farside
• Low-frequency radio astronomy <30 MHz
• Very long baseline interferometry

The Namesake – Harald Friis (1893-1976)

Radio Astronomy Background

Sacred Silence – The Far Side of the Moon

Chang’e 4 – First Farside Radio Observatory

Some LFRT Concepts in Development

Lunar Crater Radio Telescope (LCRT)

• 3-5 km wide crater
• 1 km diameter reflector, origami-style unfurling
• Rover deployment

Farside Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE)

• 128 antennae in 10 km diameter array
• Base station comm to lunar orbiter (Gateway)
• Rover deployment

FRIIS Lander Overview

• 4 landers stacked in one launcher
• Minimal payloads to conserve mass
• 3-axis low-frequency antennas
• Deployable, at least 5 m long
• Very long baseline interferometry
• Uplink to orbiter (i.e. Gateway) via X or Ka-band (>> VLF)
• Stringent EMI/EMC requirements and design practices

Mockup with help from DALL-E and PowerPoint

FRIIS ConOps Example

Stacked Launch+Cruise

Prime Landing Area: Mare Moscoviense

~90dB shielding, 276 km diameter, away from south pole

EDL Separation

Radio Interferometry�<30 MHz

Uplink to orbiter� X or Ka-band

Capability Comparison (not to scale)

• Chang’e 4 – three 5m dipoles, single lander
• LCRT – one 1km diameter dish in a 3-5km crater
• FARSIDE – 128 dipoles in 10km diameter array
• FRIIS – four 3-axis >5m antennas in 100+km diameter array

FRIIS proposes lunar large-scale VLBI far away from eventually occupied and RF-contaminated lunar south pole!

LCRT

Chang’e 4

FARSIDE (site TBD)

FRIIS

EMI Constraints

• Tight, tailored conducted+radiated emissions requirements, especially VLF to HF range 10 kHz to 30 MHz
• Very difficult due to clocks, power converter, and many data interfaces operating in this range!
• High data rates and fast rise times contain tremendous RF spectra

MIL-STD-461G RE102 Limit for Space Applications

20dB margin for LF RE is ideal

Addressing EMI Challenges

Design Mitigations

• RF tight avionics vault/Faraday cage
• Extensive filtering in+out of vault, especially solar array
• Elaborate shielding of enclosures and harnesses
• Reduction of apertures and unintentional antennas
• Decouple frequencies and lengthen rise times, when possible

Programmatic/Operational Mitigations

• Thorough characterization of FRIIS’ emissions
• Data averaging and filtering with long exposure scans

Design Trades

• Interferometer performance
• Antenna performance, deployment
• Mass conservation
• Additional payloads, if any

Detailed trade studies in later slides

Chang’e 4 Payload Suite

Antenna Trade Study

• Type
• Monopole – needs ground plane
• Dipole – 2nd element acts as ground plane
• Dish – too small for lander architecture
• Length
• Μore length, lower frequency – ≤10 m, each pole 5m
• Comparison to Chang’e 4 (5m each)
• Mechanical support likely
• Deployment
• Telescopic – antenna elements
• Foldable – use for supports

Europa Clipper REASON HF Antenna Deployment Test (8.5 m)

Dipole

Antenna Pattern

Mass Trade Study

• Difficult to sell a mission with multiple launches → fit 4 landers into 1 launch fairing
• Propulsion, GNC/EDL, support structure mass to be considered
• Additional payloads are possible

CHASE Opportunities

• Commercial Lunar Payload Services Program ($2.8b through 2028)
• FRIIS also fits as a later-term Artemis mission
• Engage private sector for RFPs
• Different farside radio telescope variants available
• Solid parabolic antennas with steerable feeds

Further Challenges & Work

• RF encroachment from orbit and nearside, especially south pole
• Space environment: thermal, radiation, regolith, and electrical reliability
• Expand interferometer baseline with more telescopes, collaboration

FRIIS the Day

Questions?

References

• “What are radio telescopes?,” National Radio Astronomy Observatory, 27-Nov-2019. [Online]. Available: https://public.nrao.edu/telescopes/radio-telescopes/. [Accessed: 12-Dec-2022].
• “Harald T. Friis,” ETHW, 04-Dec-2019. [Online]. Available: https://ethw.org/Harald_T._Friis. [Accessed: 12-Dec-2022].
• “The Wisdom of Harald Friis,” SMECC. [Online]. Available: https://www.smecc.org/harald_friis.htm. [Accessed: 12-Dec-2022].
• “Radioastronomy science from the moon - esa science &amp; technology.” [Online]. Available: https://sci.esa.int/documents/34375/36249/1567260083880-ESA-CAS-workshop1_poster7_Radioastronomy-Science-from-the-Moon_P-Zarka.pdf. [Accessed: 12-Dec-2022].
• S. Bandyopadhyay et al., “Lunar crater radio telescope (LCRT) on the far-side of the Moon,” NASA, 19-Sep-2020. [Online]. Available: https://trs.jpl.nasa.gov/handle/2014/53976. [Accessed: 12-Dec-2022].
• J. Burns et al., “FARSIDE Probe Study Final Report,” Probe-class Concept | FARSIDE: A Low Radio Frequency Interferometric Array on the Lunar Farside | University of Colorado Boulder, Nov-2019. [Online]. Available: https://www.colorado.edu/project/lunar-farside/probe-class-concept. [Accessed: 12-Dec-2022].
• P. McGarey et al., “How to deploy a 10-km interferometric radio telescope on the Moon with just four tethered robots,” arXiv.org, 06-Sep-2022. [Online]. Available: https://arxiv.org/abs/2209.02216. [Accessed: 12-Dec-2022].
• X. Zhu et al., “Ground experiments and performance evaluation of the low-frequency radio spectrometer onboard the lander of Chang'E-4 Mission,” arXiv.org, 08-Dec-2020. [Online]. Available: https://arxiv.org/abs/2012.04347. [Accessed: 12-Dec-2022].
• J. Zhou et al., “Interference Mitigation for LFRS onboard Chang'e-4,” 中科院国际会议服务平台, 28-Jul-2021. [Online]. Available: https://ram2021.casconf.cn/static/1392329320747372545/pages/file/16a9a1a6101841c7a8efd720b3766595.pdf. [Accessed: 13-Dec-2022].
• Y. Su et al., “In-orbit Performance of Chang’e-4 Low Frequency Radio Spectrometer,” CO Meeting Organizer EPSC-DPS2019, 15-Sep-2019. [Online]. Available: https://meetingorganizer.copernicus.org/EPSC-DPS2019/EPSC-DPS2019-529.pdf. [Accessed: 13-Dec-2022].
• “MIL-STD-461G, Department of Defense Interface Standard: Requirements for the control of electromagnetic interference characteristics of subsystems and equipment (11-Dec-2015),” EverySpec Standards, 11-Dec-2015. [Online]. Available: http://everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461G_53571/. [Accessed: 12-Dec-2022].
• F. Leferink, “Shielding,” in 2022 IEEE International Symposium on Electromagnetic Compatibility & Signal/Power Integrity (EMCSI), 2022.

BACKUP

Abstract

The lunar farside is the dream destination for radio astronomy. Substantially shielded from solar, terrestrial, and human interference, the far side of the moon provides the best vantage point to detect low frequency (<30 MHz) radio signals. The science potential is palpable, with multiple missions in development (and one in operations) to send a radio telescope there. Some of these concepts include interferometry, which augments radio telescopes’ scale and capability. The current farside radio observatory’s operations were impacted due to its spacecraft’s own electromagnetic interference.

The Farside Radio Interferometer In-Situ (FRIIS) addresses these challenges with a mission consisting of an array of radio telescope landers. These observatories would be strategically positioned to create a larger yet more reliable radio telescope than the existing architectures. Extensive electromagnetic compatibility requirements and design guidelines will be explored. Payload design trades will also be discussed.

Bio & Picture

Manuel Martin Soriano is an electromagnetic compatibility engineer at NASA Jet Propulsion Laboratory/Caltech. Currently, he leads the EMC and magnetic cleanliness efforts for the Psyche mission as well as JPL’s various ISS payloads (CAL, ECOSTRESS, EMIT, OCO-3, SAM). Additionally, he supports environmental assurance efforts for Earth science missions and various R&D efforts. He obtained his B.S. Electrical Engineering from University of Southern California, where he is also working on a M.S. in Astronautical Engineering.

Additional Concepts Explored

• Crewed Orbital Debris Control
• High-Data Link between Earth and Mars
• LEObnb
• Lunar EMI control*
• Lunar Healthcare*
• Lunar Regolith Management
• Next Generation ISS

*Pitched during 9/27/22 “Alternative Ideas” class session with LFRT concept

Graceful Degradation / Maintain Long Baseline

3 Lander VLBI

2 Lander VLBI

Farside Radio Telescope Concepts

• Chang’e 4
• Dark Ages Lunar Interferometer (DALI)
• ESA Lunar Lander
• FARSIDE
• Farside Explorer
• LCRT