Article Figures & Data
Figures
- FIGURE 1
Block diagram of Iris radio signal processing for forming one-way uplink radiometric data
- FIGURE 2
Iris DDC
- FIGURE 3
1σ range error uncertainty from the Iris STL for various loop bandwidths as a function of range signal power to noise (Pr/No)
- FIGURE 4
Difference between Iris time and CSAC time (left) and the second difference (right)
- FIGURE 5
Raw total count phase
- FIGURE 6
OADs of the raw total count phase, the same phase with its frequency drift removed, and the calibrated phase for Method 1, all normalized by the carrier frequency
- FIGURE 7
One-way range rate uncertainty as determined using Method 1
The theoretical result is computed using the RSS of Equations (41)–(43), and the experimental result is the standard deviation of the range rate residuals after the removal of deterministic biases, rates, and accelerations.
- FIGURE 8
OAD of the range rate computed using Method 1 for selected integration times
- FIGURE 9
Range rate results for Method 1 with T =1 s; range rate from the uncalibrated phase (top), calibrated range rate (middle), and calibrated range with bias, rate, and acceleration effects removed (i.e., “detrended”) (bottom)
- FIGURE 10
Histogram of the calibrated, detrended range rate for Method 1 with T =1 s
- FIGURE 11
Range rate results for Method 1 with T =60 s; range rate from the uncalibrated phase (top), calibrated range rate (middle), and calibrated range with bias, rate, and acceleration effects removed (i.e., “detrended”) (bottom)
- FIGURE 12
Histogram of the calibrated, detrended range rate for Method 1 with T =60 s
- FIGURE 13
Prefit clock residuals (top) and postfit residuals (bottom)
- FIGURE 14
OAD of the clock filter prefit residuals (blue), postfit residuals (orange), clock phase solution (green), and normalized raw total count phase (red)
- FIGURE 15
OADs of the raw total count phase (blue), the same phase with its frequency drift removed (orange), the calibrated phase based on Method 2 (green), and, for comparison, the calibrated phase based on Method 1 (red), all normalized by the identified carrier frequency
- FIGURE 16
One-way range rate uncertainty as determined via Method 2
The theoretical result (orange dash–dot curve) is computed from Equation (60), and the experimental result (blue curve) is the standard deviation of the range rate residuals after the removal of deterministic biases, rates, and accelerations. Experimental results for Method 1 (green curve) are shown for comparison.
- FIGURE 17
OAD of the range rate computed from Method 2 for selected integration times
- FIGURE 18
Range rate results for Method 2 with T =1 and 60 s
The top and bottom left images are for T =1 s, and the top and bottom right images are for T =60 s. Top plots show the range rate from the uncalibrated phase (top), calibrated range rate (middle), and calibrated range with bias, rate, and acceleration effects removed (i.e., “detrended”) (bottom) for their respective integration times. Bottom plots show an associated histogram of the calibrated and detrended range rates.
- FIGURE 19
Iris TCXO range results: raw (upper left) and detrended (lower left); CSAC range results: raw (upper right) and detrended (lower right)
- FIGURE 20
OAD of the raw CSAC range (blue) and raw Iris TCXO range (orange), which have both been normalized to time by dividing by the speed of light; CSAC (green) and TCXO (red) OAD derived from total count phase measurements
- FIGURE 21
Iris CTL
- FIGURE 22
Iris STL used for ranging demodulation in the discrete time domain (top) and a continuous linear representation in the s-domain where VCO is a voltage controlled oscillator (bottom)
Tables
Field Name Size Description 1PPS Count 4 bytes Running integral count of 1PPS seconds, which can accumulate up to 232 seconds (or approximately 136 years) Iris Time (seconds) 4 bytes Count of seconds since Iris was turned on based on TCXO ticks; increments each time the subseconds counter rolls over Iris Time (subseconds) 4 bytes Count of 50-MHz TCXO ticks; rolls over to 0 after 49,999,999 Total Carrier Phase (TCP) 8 bytes Integral number representing the total count phase since carrier lock; determines a floating-point estimate of phase cycles using 
Allan Deviation σy(T) a σWF σRWF Iris TCXO (Q-Tech Q804) Spec value: σy(1) < 1 × 10−19
8.1 ×10−9/day – 2.4 ×10−8/day Measured values: σy(1) = 4 × 10−11
σy(100) = 5 × 10−11
σy(1000) = 2 × 10−10
σy(10000) = 2 × 10−9
(Variation as seen with measured OAD for different tests) (Derived from measured OAD) (Derived from measured OAD) CSAC SA-45S Spec values: σy(1) = 3 × 10−10
σy(10) = 1 × 10−10
σy (100) = 3 × 10−11
σy(1000) = 1 × 10−11
(Derived from specified OAD)
(Derived from specified OAD)
(Derived from specified OAD)Measured values: Unknown
Field Name Size Description PN Epoch Count 4 bytes Index of PN epoch; increments each time PN chip 0 is received; count begins when the PN ranging correlators are locked; resets to 0 when lock is lost; rolls over to 0 after 65,535 PN Chip Index (q) 4 bytes PN component sequence delays; can be used to calculate index of current PN chip (0 to 1,009,469) using the Chinese remainder theorem; valid when PN ranging correlators are locked PN Chip Accumulator (PCA) 8 bytes PN symbol clock phase accumulator from the STL; accumulation begins when the PN ranging correlators are locked; determines a floating-point estimate of the fractional chip phase using ETT Epoch 4 bytes PN epoch count to which the current value of the ETT register belongs ETT 4 bytes 32-bit ETT; bit 31 corresponds to the bit encoded in PN chip 0 of the epoch reported in the ETT epoch register - TABLE 4
Estimated Fractional Frequency Offsets and Aging for the Iris TCXO and CSAC Determined From Range
Iris TCXO 6.07 × 10−7 s/s, 1821 m/s 8.1 × 10−9/day, 2.8 × 10−5 m/s2 CSAC 1.50 × 10−9 s/s, 0.45 m/s 5.8 × 10−11/day, 2.0 × 10−7 m/s2
Jump to section
- Article
- Abstract
- 1 INTRODUCTION
- 2 IRIS RADIO RECEIVER SIGNAL PROCESSING TO OBTAIN THE TOTAL COUNT PHASE
- 3 FORMING THE RANGE RATE MEASUREMENTS
- 4 IRIS RADIO RECEIVER SIGNAL PROCESSING TO OBTAIN RANGE
- 5 RANGE RATE RESULTS FROM THE TWO METHODS
- 6 RANGE RESULTS
- HOW TO CITE THIS ARTICLE
- ACKNOWLEDGEMENTS
- APPENDIX A: IRIS CARRIER PHASE NOISE VARIANCE
- APPENDIX B: IRIS SYMBOL TIMING VARIANCE
- Footnotes
- REFERENCES
- Figures & Data
- Supplemental
- References
- Info & Metrics
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