Deep Space Atomic Clock Advancing Navigation & Science

National Aeronautics and Space Administration

Principal Investigator: Todd Ely Co-Investigators: Robert Tjoelker, John Prestage

NASA’s DSAC Technology Demonstration Mission Technology Performance and Operation

DSAC Demonstration Unit (CAD) Output Light Error Signal! System!

Linear Ion Trap! −12 Multi-pole Trap Mercury UV Lamp Testing 10 TDM required performance in the space environment Quadrupole Trap Local AD of 1.e-14 @ 1-day −13 Oscillator! Microwave 10 Input Light User Output input @! System! Synthesizer! 40.5 GHz!

Titanium Vacuum Tube −14 Uncontrolled Input Frequency ! 10 Stable Output Frequency ! Current estimated performance to Transmitter/Receiver!

Overlapping Allan Deviation in the space environment @ XX MHz! −15 10 Ion Clock Operation AD of 2.3e-15 @ 1-day • Short term (1 – 10 sec) stability depends on Local Oscillator −16 (DSAC’s USO 2e-13 at 1 second) 10 2 3 4 5 Develop advanced prototype (‘Demo Unit’) mercury-ion atomic clock for navigation/science in deep space and 10 10 10 10 Earth • Longer term (> 10 sec) stability determined by “atomic (sec) resonator” (Ion Trap & Light System) yields AD < 3.E-15 at 1- Ion Clock Technology Highlights • Perform a year-long demonstration in space beginning in 2016 – advances the technology to TRL 7 day • State selection of 106-107 electric-field contained (no wall • Focus on new technology maturation – ion trap and optical systems – other system components (i.e. Key Features for Reliable, Long-Life Use in Space payload controllers, USO, GPS) size, weight, power (SWaP) dependent on resources/schedule collisions) 199Hg+ via optical pumping from 202Hg+ • No lasers, cryogenics, microwave cavity, light shift • Identify pathways to design a smaller, more power efficient future operational unit (TRL 7 → 9) • High Q microwave line allows precision measurement of clock • Low sensitivities transition at 40,507,347,996.8 Hz with Mission Architecture - Temperature 7e-16/C @ 1-day • Ion shuttling from quadrupole to multipole trap for best - Magnetics 3e-15/G @1-day Launch May 2016 with one-year demonstration! disturbance isolation GPS Sat 1 - Voltage 3e-16/V @ 1-day • Ions in an uncooled Neon buffer-gas SST-US Orbital Test Bed Crosscutting Infusion Customer Base

Near Space Navigation/ Deep Space Navigation Science Deep Space Timing Autonomy DSAC Timing Hosted GPS Sat 2 Payload USAF – SMC/GPS NASA IND/DSN NASA SMD/PSD NASA IND/DSN NASA SMD/PSD range & phase USAF – MILSATCOM NASA SMD/PSD NASA SMD/PSD NRO Commanding & • Diversify clock industrial • Multiple Spacecraft Per • Enhance gravity science • Significantly reduce • Enables autonomous Telemetry base - enhancing national Aperture at Mars - doubles - at Mars, GRACE-level spacecraft timekeeping radio navigation (robotic security useful tracking determination of long term overhead and crewed) SST-US • Improve GPS clock • Full use of Ka-band gravity with one satellite • Improve reliability of • Enhances EDL and Ground performance tracking – OD uncertainty - at Europa, flyby gravity critical time-dependent precision landing Network GPS Sat n • Provide time accuracy/ at Mars < 1 m (10x objectives met robustly autonomous spacecraft • Key component to stability needed for next improvement) • Enhance planetary occultation functions autonomous aerobraking sftp JPL GNSS Service (IGS): generation secure • Outer planets users gain science with 10x better data • Reduce risks to long- • Coupled with OpNav, - ~ 400 GPS tracking stations globally communications significant tracking term spacecraft enhances primitive body - USNO reference with < 1.e-15 steered stability • Aid users with efficiency hibernation exploration DSAC compromised GPS - 15% at Jupiter Investigation Team visibility – only 3 in-view - 25% at Saturn USAF STP II needed to position (Falcon Heavy) Example Use: MSPA Tracking of Mars Orbiter Result: Improvements to Mars Navigation and Gravity Science

DSAC enabled 1-Way average improvement on 2-way navigation DSAC enabled 1-Way average improvement on 2-way gravity solution Two−Way Tracking Schedule • X-band: 1.4x (MSPA) • X-band: 2x (MSPA) DSN transmits to one spacecraft at a time, but Madrid • Ka-band: 5.1x (MSPA and 10x better data) • Ka-band: 12x (MSPA and 10x better data) is capable of receiving signals from two 2W X, 1W X w/ DSAC, 1W X w/ USO, 1W Ka w/ DSAC spacecraft simultaneously (MSPA) 1.0 3 • Plans to upgrade to 4 simultaneous 2−way X Canberra 0.1 1−way X, DSAC downlinks 0.01 2 1−way Ka, DSAC 9) − Radial (m) 0.001 0 5 10 15 20 25 30 35 40 Goldstone 2-way tracking suffers lengthy tracking gaps 0 10 20 30 40 50 1 10 when DSN committed to tracking other One−WayTracking Schedule spacecraft Madrid 1 0 • Gaps may persist on order of 8-10 hours

0.1 Gravity Term and will increase with arrival of MAVEN Tangential (m) 0 5 10 15 20 25 30 35 40 −1 Canberra 100 sigma Uncertainty (x1e − 10 3 −2 1-way downlink tracking exploits MSPA 1 capability è signal is available anytime an Goldstone 0.1 0 10 20 30 40 50 Normal (m) 0.01 −3 antenna is pointed at Mars Time (hr) 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 80 Time (hr) Gravity Terms

Example Use: DSAC-Enabled LGA Tracking in Deep Space Result: Improvements to Europa Gravitational Tide Estimation Using DSAC for Your Mission

DSN Coverage of Europa Flybys, Three Fanbeams 0.3 2−way w/ 3 Fan Beams, DSN Depending on intended use, 2-Way closed-loop tracking 2 2−way w/ 3 Fan Beams, DSN + ESA environments, etc…two options for across deep space requires very 0.25 1−way w/ 3 LGAs + DSAC, DSN large signal-to-noise 1 Fan beam implementation exist: coverage 1−way w/ 3 LGAs + DSAC, DSN, Alternate Traj • Small Field of View can limited even 0.2 0 DSAC As-Is DSAC Reduced significantly limit HGA access when optimally • SWaP: 17 kg & 56 W • SWaP: 10 kg & 30 W 0.15 Alternate trajectory not

Open-loop tracking may be −1 Uncertainty (with the USO) Time Relative to positioned optimized for gravity science Close Approach (hr) performed via either Medium − • Typical engineering 1

Gain Antennas (MGAs) or Low 22 0.1 • GEVs dynamics effort to repackage

−2 k electronics and Gain Antennas (LGAs) DSN Coverage of Europa Flybys, Three LGAs • Functionality & integrate the USO • MGAs è 2-way link 2 Liquid ocean 0.05 determination threshold usability proven in • LGA è 1-way uplink 2016 mission • Use DSAC As-Is ion- 1 LGAs 0 trap and optical provide 0 5 10 15 20 25 30 35 40 45 systems nearly Flyby Number 0 LGA + DSAC enables continuous high-quality uplink-only • Europa gravitational tide parameters can confirm subsurface liquid ocean existence For both options, analysis of 1-way uplink • Solution quality inherently limited by quantity/quality of available tracking data tracking data −1

Time Relative to environments and lifetime would be access • DSAC-enabled LGA solution satisfies science requirement early in primary mission – Close Approach (hr) robust to missing key flybys and/or trajectory redesign required −2 Flybys

National Aeronautics and Space Administration

Jet Propulsion Laboratory California Institute of Technology Pasadena, California www.nasa.gov

! 2014 California Institute of Technology. Government sponsorship acknowledged.