Interplanetary and Interstellar Communication and Navigation Prof. Philip Mauskopf Arizona State University Cosmology instrumentation Superconducting detectors Optical Communications Technologies Mission Ops for SPHEREx

FISW 2019 Wotton-Under-Edge Navigation questions: 1. If we could build an interstellar propulsion system, can we navigate between the ? • Yes – there are many possible technologies (e.g. Richards, JBIS, 28, 1975, Smith, Sheikh and Swinney, JBIS, 69, 2016). This is an easier problem than getting close to light speed but there are details to be worked out: • What are the best navigation tools for interstellar travel? • What are the mass and power requirements? 2. Can we navigate the tiny flyby probes (e.g. Breakthrough Starshots) to the nearest stars and obtain images of ? • Hopefully yes but this is a more difficult problem because of the extreme mass and power constraints. There are lots of questions and trade-offs, e.g. • Do we need on-board navigation? • What communication links are needed during the trip for course correction? Communication questions: 1. Can we communicate with interstellar spaceships? • Yes – there are many possible technologies but there are details to be worked out: • What are the best communication tools? • What are the mass and power requirements on board and at the home base? 2. Can we send and receive images from the tiny flyby probes (e.g. Breakthrough Starshots) at the nearest stars? • Hopefully yes but this is a more difficult problem because of the extreme mass and power constraints (see Lubin, Messerschmidt and Morrison, 2018). There are lots of questions and trade-offs, e.g. • What is the power source on board? • How do we focus and point a signal towards the earth? • Etc. Technologies for Deep Space Navigation

• trackers • Relative positions and periods of objects in (e.g. , planets, binary stars, transits, etc.) • Clocks • Doppler/lighthouse velocity measurements • Radio sources • Earth-based radio Orientation: • Radio pulsars Which way am I • Artificial radio pulsars • Radio extragalactic background (e.g. CMB) pointed? • Optical to X-ray • Optical or X-ray pulsars • Artificial optical pulsars • Stellar colours and magnitudes or absorption lines • Range finding • One or two way light travel time • Sizes and separation of objects – e.g. stars Technologies for Deep Space Navigation

• Star trackers • Relative positions and periods of objects in orbits (e.g. moons, planets, binary stars, exoplanet transits, etc.) • Clocks • Doppler/lighthouse velocity measurements Position: • Radio sources Where am I • Earth-based radio • Radio pulsars with respect to • Artificial radio pulsars • Radio extragalactic background (e.g. CMB) my origin • Optical to X-ray /destination? • Optical or X-ray pulsars • Artificial optical pulsars • Stellar colours and magnitudes or absorption lines • Range finding • One or two way light travel time • Sizes and separation of objects – e.g. stars Technologies for Deep Space Navigation

• Star trackers • Relative positions and periods of objects in orbits (e.g. moons, planets, binary stars, exoplanet transits, etc.) • Clocks Velocity: Which • Doppler/lighthouse velocity measurements • Radio sources way am I going • Earth-based radio • Radio pulsars and how fast? • Artificial radio pulsars • Radio extragalactic background (e.g. CMB) • Optical to X-ray • Optical or X-ray pulsars • Artificial optical pulsars • Stellar colours and magnitudes or absorption lines • Range finding • One or two way light travel time • Sizes and separation of objects – e.g. stars Navigation on or around Earth

Predominantly uses GPS: • System of in medium earth • Trilateration (range finding) • Equipped with atomic clocks • Three satellites give X, Y, Z – need fourth to close loop and also get time • Small hand-held devices Deep Space Navigation in the

Currently uses: • Radio Doppler and range finding with DSN • Orientation and location with images of stars and solar system objects (e.g. planets, moons and asteroids) • Near-object navigation with imaging of destination target and autonomous software • Need for more standardisation and automation for future solar system travel Deep Space Positioning System (from Caltech/JPL) The proposed solution DPS: Deep Space Positioning System

• Develop a multi-use instrument capable of: – Navigation measurement (optical and radio) – Data processing and orbit determination – Path planning and maneuver estimation – Course correction implementation • Make the hardware and software generally applicable enough that: – Only moderate (if any at all) modifications would be required for each particular mission Joseph E. Riedel, Joseph R. Guinn, Shyam Bhaskaran, Ryan S. Park, Andrew T. Vaughan, William M. Owen, Todd A. Ely, Matthew Abrahamson, Tomas J. Martin- Mur from SCAN Workshop on Autonomous Navigation

DPS: Deep Space Positioning System 14 Deep Space Positioning System (from Caltech/JPL) Elements of the DPS concept Camera, radio, clock, steering actuators and flight software Integrated DPS Instrument

Iris Software Defined Radio Extracts one-way radio observables and hosts AutoNav FSW

MRO OpNav Camera 2.1° FOV high-sensitivity camera

ASC Star-tracker Deep Impact AutoNav STMD Deep Space Atomic Clock OCO-3 Actuators Provides autonomous in situ Provides “DSN-Quality” frequency and time navigation (via optical and/or radio) reference for one-way radio DPS: Deep Space Positioning System 15 Joseph E. Riedel, Joseph R. Guinn, Shyam Bhaskaran, Ryan S. Park, Andrew T. Vaughan, William M. Owen, Todd A. Ely, Matthew Abrahamson, Tomas J. Martin-Mur from SCAN Workshop on Autonomous Navigation Deep Space Atomic Clock (DSAC): NASA/JPL

Mass 17.5 kg Operating specs: Dimensions 29 × 26 × 23 cm • Uses Hg ion transition in (11 × 10 × 9 in) microwave cavity at 40.5 GHz Number launched 1 • No cryogenics or -15 Power consumption 44 W • Stability ~ 3 x 10 at one day (~ 1 nanosecond) Launched Tuesday on • ~ 50x more accurate than SpaceX Falcon Heavy current GPS clocks Proposal for Deep Space Positioning System in the Solar System Similar to GPS: • Fly multiple satellites with radio or optical beacons and on- board DSACs • Spread them throughout the solar system • Emission will be in the plane of the solar system • Act like artificial pulsars – positions monitored by DSN just like GPS • have small DPS receivers and are independent of earth ground stations Earth Orbiting Radio Beacons

• GPS satellites • Radio transmitters • Atomic Clocks • Time and location references • MEO (~20000 km) • Precision limited by on-board clocks, drag, gravity flucutations, atmosphere, etc. Solar System Beacons

• Antenna or dish emitting in the ecliptic plane • Pulsed /RF – On-board atomic clocks (like GPS) – Pulsed or modulated RF or laser signal (like GPS) • Spinning laser/RF – No atomic clock needed (but still could be used to generate emitted signal) – Miniature pulsars Solar System Beacons for navigation

• Detectable by interplanetary spacecraft with on-board antenna • Provides information about location and velocity (complements star camera information about orientation) • Autonomous navigation – no need for guidance from earth, faster response time, etc. Comparison with Natural Radio Pulsars

• Brightest radio pulsar ~ 1 Jy peak pulse • 10 Watt transmitter on pulsat (pulsar ) • Assume 50% modulation at 90 GHz in a 1 Hz bandwidth with a 60 cm dipole antenna – Beam size is 2p x 1/200 sr – Peak power at 5 AU on a 10 cm diameter dish = 6 x 10-24 W à 60000 Jy – Noise power is about 5 x 10-22 W in a 1 Hz bandwidth so not quite enough power to have a small receiver Galactic Beacons for Interstellar Navigation

Pulsars • Orbital period -> stable time reference • Known sky location gives position reference • Can be used for navigation • Radio signal strength is weak ~ 1 Jy peak for the brightest pulsar so you need a big dish to detect • Optical signal is also weak (brightest ~ 16th magnitude = Crab) • X-ray signals are stronger but fewer photons and require large detectors (e.g. SEXTANT – demo on NICER) Galactic Beacons for Interstellar Navigation Pulsars can also be used for gravitational wave detection Extragalactic Beacons/Reference frames Cosmic Microwave Background or Extragalactic Backgrounds • Traveling at 0.2c there will be a dipole temperature anisotropy in the Cosmic Microwave Background (CMB) of ��~ 550 �� • A small passively cooled coherent radiometer with 10 GHz bandwidth at any frequency where the CMB is dominant (i.e. 30 GHz – 200 GHz) can have a noise temperature of < 100 K and temperature sensitivity of < 1 mK � • Can measure the CMB dipole with high signal to noise very quickly and get velocity direction and speed • Use a phased array on light sail to improve angular resolution Other Relativistic effects

Relativistic image distortion • Objects in front will appear to be smaller or closer together and objects behind will be spread out • Can use a regular star camera and compare positions in the image with fiducial positions at rest and determine velocity and orientation • For the AB Centauri system, can use the

separation between the stars to measure distance Two photographs of the gate. Top: The camera is at rest. Bottom: The camera approaches the gate at 90% of the c. Both photographs are taken at the same distance to the gate (see sketch). The camera is looking towards the gate. https://spacetimetravel.org Interstellar Communications: e.g. Sending images of planets from

1. Can we communicate with interstellar spaceships? • Yes – there are many possible technologies but there are details to be worked out: • What are the best communication tools? • What are the mass and power requirements on board and at the home base? 2. Can we send and receive images from the tiny flyby probes (e.g. Breakthrough Starshots) at the nearest stars? • Hopefully yes but this is a more difficult problem because of the extreme mass and power constraints. There are lots of questions and trade-offs, e.g. • What is the power source on board? • How do we focus and point a signal towards the earth?

• Proposal to send ”wafer” satellites to nearest star with known (Proxima Centauri), 4.24 light years away • Based on ideas from various people (including Phil Lubin) to use coherent to accelerate satellites with light sails • Funded by Yuri Milner (also Breakthrough Prizes and Breakthrough Listen) • Goal – 0.2 c travel speed ~21 years travel time • Launch in ~20 years à time to develop the technology • Coherent 200 GW laser • Lightweight sail that won’t burn or mechanically break apart • Navigation and communication solutions to arrive at target, take pictures and send back data Navigation for Flyby or Orbit insertion Example: New Horizons

• 30 AU distant from Earth flyby of Pluto • Navigation by two way Doppler distance and velocity measurements plus on board accelerometers with integrated velocity accuracy of a few mm/s plus on board star cameras with 1 arc second resolution. • “precise measurement of the velocity change associated with propulsive maneuvers is necessary in order to predict the trajectory of the spacecraft. A one millimeter per second velocity error will map into a spacecraft position error of over a kilometer in 10 days” from New Horizons Navigation to Pluto in Advances in Astronautical Sciences, 2008. New Horizon’s trajectory:

• Closest approach: 7750 km • Speed: 0.00004 c • Distance from earth: 30 AU = 0.000005 ly New Horizon’s images: Pluto

• Closest approach: 7750 km • Speed: 0.00004 c • Distance from earth: 30 AU = 0.000005 ly New Horizon’s images: Charon • Closest approach: 15000 km • Speed: 0.00004 c • Distance from earth: 30 AU = 0.000005 ly

Charon New Horizon’s images: Pluto spectra (with LVF)

• Closest approach: 7750 km • Speed: 0.00004 c • Distance from earth: 30 AU = 0.000005 ly Navigation and Communcation for Probe Mission to Proxima Centauri: • Many unsolved problems • Power source • Navigation and course corrections – how do you arrive at the target? • Acquiring images during flyby • Sending image data back - communications • First focus on getting images back from 4.24 light years • Current technology = radio communications • Next generation = optical communications • Deep Space Optical Communications instrument to be flown on NASA Psyche mission (ASU is PI institute) • is Palomar 5 meter telescope with 64 element superconducting nanowire single photon detector array

DSOC SystemDeep Space Optical Communications

Point Thermal Ahead Monitor & Mirror Control (PAM) (TMC)

NASA/JPL demonstration IR laser communications Optical Transceiver Floating Assembly (OTA) Photon Counting Platform Stationary Ext. I/F Camera (PCC) Electronics Platfrom system for the Psyche mission to be launched in (FPE) Electronics Deep-Space Optical (SPE) Communications Laser Collimator FLT (DSOC) 2022: Electronics Box Laser Transmitter Flight Laser Isolation Pointing Assembly Transceiver (FLT) Assembly Optical Head (IPA) (LTA) On board Laser Transceiver4W, 22 cm dia. Data/Pwr Virtual presence throughout the solar system 1064 nm Optical Fiber Beacon & Uplink Max rate 1 kb/s Photo/Drawing• 22 cm diameter mirror aperture

Ground Laser Transmitter (GLT) Deep Space OTA Table Mtn., CA Network 1m-OCTL• Telesc4 W laser at 1.55 umope (5 kW) (DSN ) Ground Laser Receiver (GLR) Palomar Mtn., CA 5m-dia. Hale Telescope • Mass < 38 kg FPE Optical Comm Ops Ctr. . Mission •. Ops Power < 100 WCenter PCC

IPA

Flight Laser Transceiver 4 Deep Space Optical CommunicationsDSOC Major Components OCTL Uplink DSOC Major Components OCTL Uplink DSOC Ground Station Uplink Flight Terminal Flight Terminal • OCTL Telescope (1 meter) • 5 kW average power • Wavelength 1.064 microns TRL 6 Demo Downlink Palomar 5 meter Telescope • Palomar 5 meter telescope Palomar 5 meter Telescope • GROUND DETECTOR • Operates day or night • Tungsten silicide (WSi) SNSPD Detector Array _ Verified 12-pixel array (Eff. dia. 65 μm) during LLCD • Can point within 12 degrees of _ In FY14 demonstrated 64-pixel array (Eff. dia. 160 μm) _ Developing 320 μm, 64-pixel array • JPL developed superconducting • GROUND SUPPORT EQUIPMENT (GSE) nanowire single photon _counting Simulate _ Spacecraft disturbance 320-μm, 64 pixel WSi SNSPD Array detector _ Anti-gravity suspension _ Ground beacon laser _ Ground Receiver April 27, 2015 Interplanetary Network Directorate Strategy

TVACChamber 1E-6 Torr April 27, 2015 Interplanetary Network Directorate Strategy 0 to 25C Operational With Optical Access & -15 to +45C Survival Shrouds (not shown) Gravity Off-Load Anti-Gravity Suspension of Suspension OPTICAL TRANSCEIVER ASSEMBLY (OTA) (Optical Transceiver + PAM + Laser Collimator+FPE)

Beacon 1550 nm 1064 nm Downlink FPE

OTA Provides Laser SPE Point-Ahead Isolation Pointing Assy. Optical Transmitter Measurement (IPA) Fiber Capability Disturbance Emulator 11-foot Thermal-Vacuum Data/Pwr Chamber Optical communications parameters: Subset of parameters for “standard” communications (see Lubin, Messerschmidt and Morrison, 2018):

Dsail = diameter of light sail (assume it is used to focus light towards Earth) or other on-board aperture

Adishes = collecting area of telescopes near or on Earth

� = frequency of light

∆� = bandwidth of light

Pemit = power emitted at Proxima “Optical” communications: Subset of parameters for “standard” communications (wavelength independent):

Dsail , Adishes , �, ∆�, ℓ = distance to Proxima

� = photon occupation number at receiver(s) = photons/sec/Hz/mode (unitless)

� � � � = � ℎℓ� ∆�

Want � > 1 to detect signal with number of bits per second ~ ∆� (assuming fundamental noise limits either photon shot noise from source or amplifier quantum noise) “Optical” communications: Example for 1.55 um communications with DSOC (sanity check):

Dsail = .22 m 2 Adish = 20 m (Palomar) = 4 × 10 (250 MHz bandwidth) ∆ ℓ = 3 AU = 4.5 x 1011 m � = 4 Watt

4� � � � = � = 5 ℎℓ� ∆�

Want � > 1 to detect signal (assuming fundamental noise limits either photon shot noise from source or amplifier quantum noise) “Optical” communications: Example for 1 um communications with e.g. GMT:

Dsail = 30 m 2 Adish = 1000 m (2 x 30 meter telescopes) = 10 (1 kHz bandwidth) ∆ ℓ = 4 x 1016 m � = 1 Watt

4� � � � = � = 4 ℎℓ� ∆�

Want � > 1 to detect signal (assuming fundamental noise limits either photon shot noise from source or amplifier quantum noise) “Optical” communications: Example for 1 um communications with optical SKA: Need 107 single photon detectors with total < 1 dark count per second. Could be background limited by dark matter (Hochberg, et al. https://arxiv.org/pdf/1903.05101.pdf)

Dsail = 30 m 2 Adish = 1000000 m = 10 (1 kHz bandwidth) ∆ ℓ = 4 x 1016 m � = 10 mWatt

4� � � � = � = 40 ℎℓ� ∆�

Want � > 1 to detect signal (assuming fundamental noise limits either photon shot noise from source or amplifier quantum noise) “Optical” communications: Example for 30 GHz communications with SKA plus ngVLA etc.:

Dsail = 30 m 2 Adish = 1000000 m (SKA) = 3 × 10 (1 kHz bandwidth) ∆ ℓ = 4 x 1016 m � = 1 Watt

4� � � � = � = 1.2 ℎℓ� ∆�

Want � > 1 to detect signal (assuming fundamental noise limits either photon shot noise from source or amplifier quantum noise. CMB occupation number at 30 GHz is > 1) “Optical” communications: • With upcoming ground-based telescopes, it would be possible to receive 10s of Hz of bits in either the optical (with 30 m telescopes) or radio (with Square Kilometer Array).

• It is easier to increase collecting area near Earth than increase transmit power or sail diameter

• Higher bandwidth optical communications would need larger collecting area with good resolution to minimize stray photons Other ideas:

• Use sail to reflect light from Proxima as it passes by and modulate reflectivity • Not enough photons (the star is too dim) • Broad band so large photon background from atmosphere

• Use propulsion laser as source and modulate reflectivity of the sail. Power at Proxima on sail ~ 1 Watt. • Laser not on all the time Science ideas:

• Measurement of absolute (cosmological) spectral features • Varying speed => shifts spectral features • Going outside solar system => changes foregrounds, e.g. zodiacal light, radio emission • Systematic check • 10% the speed of light -> spectrum shifts by 10% • Dark Matter detection (large arrays of superconducting single photon detectors with low dark count rates