Dual One-Way Ranging (DOWR)
Author: Tianjiang Says
Reference: Li Y et al. 2026 Chin. Phys. Lett. 43 031101
Website: https://cislunarspace.cn
Definition
Dual One-Way Ranging (DOWR) is a precision measurement technique that performs simultaneous uplink and downlink one-way ranging. By exploiting the opposite-signed gravitational redshift effects on the two links and using differential processing, DOWR can extract effects like gravitational redshift while canceling common error terms.
Working Principle
A DOWR system configuration:
Spaceborne PHM → TFDP → K-band Transponder → (Uplink 23 GHz) → Ground Station
↓
Ground Station → (Downlink 26.5 GHz) → Spaceborne TFDP → PHM
Key processing steps:
- Simultaneous bidirectional transmission: Ground station transmits at 23 GHz while satellite simultaneously transmits at 26.5 GHz
- Independent code pseudorange measurement: Pseudoranges for uplink and downlink are measured separately
- Differential combination: The two direction measurements are subtracted
Key advantages of differential processing:
- Common error cancellation: Common terms like satellite-ground clock offset and system delay are eliminated in the difference
- Signal enhancement: Subtraction effectively doubles the gravitational redshift signal
- Environmental interference suppression: Effects like atmospheric refraction and ionospheric delay are significantly reduced after differencing
Relation to Gravitational Redshift Measurement
In the DRO-A satellite gravitational redshift experiment, DOWR enables satellite-ground time-frequency comparison:
| Measurement Parameter | Precision |
|---|---|
| Time comparison precision | >1 ns |
| Frequency comparison stability (MDEV) | @2000 s |
DOWR is ideal for gravitational redshift measurements because:
- Gravitational redshift has opposite signs on uplink and downlink
- Differential extraction yields pure gravitational redshift signal
- Compared to triple-link schemes, DOWR reduces required links by one, lowering system complexity
K-band Selection Rationale
K-band (23/26.5 GHz) was chosen over lower frequencies because:
| Factor | K-band Advantage |
|---|---|
| Ionospheric delay | K-band is insensitive to ionosphere; TEC variations have minimal impact |
| Atmospheric attenuation | Higher atmospheric transmittance at K-band |
| Antenna size | Higher frequency allows smaller antenna aperture |
However, K-band limitations: dual-frequency systems cannot accurately determine TEC, unlike triple-frequency systems.
Applications in Other Missions
DOWR technology has been validated in multiple space missions:
- Gravity Recovery and Climate Experiment (GRACE): Satellite time transfer for gravity measurement
- Gravity Recovery and Interior Laboratory (GRAIL): Lunar gravity measurement
- BeiDou Navigation Satellite System: Inter-satellite DOWR code measurement, time synchronization precision <1 ns
Related Concepts
- Gravitational Redshift
- Passive Hydrogen Maser (PHM)
- Allan Deviation (ADEV)
- Distant Retrograde Orbit (DRO)
- Inter-Satellite Link
References
- Li Y, Liu T et al. 2026 Chin. Phys. Lett. 43 031101
- Qin C G et al. 2024 Class. Quantum Grav. 41 135006
- Kim J and Tapley B D 2003 J. Spacecr. Rockets 40 419
- Turyshev S G et al. 2013 Phys. Rev. D 87 024020