Considerations on DOR Considerations on DOR Tone Frequency and - PowerPoint PPT Presentation

Considerations on DOR Considerations on DOR Tone Frequency and Tone Frequency and Structure Structure James S. Border James S. Border Jet Propulsion Laboratory Jet Propulsion Laboratory Fall 2007 CCSDS Meeting Fall 2007 CCSDS Meeting Heppenheim, Germany, October 2, 2007 Heppenheim , Germany, October 2, 2007

Jet Propulsion Laboratory California Institute of Technology Topics to be Covered Topics to be Covered  Purpose Purpose   Description of Description of ∆ ∆ DOR DOR   Projected Navigation Requirements Projected Navigation Requirements   Limiting Error Sources by RF Band Limiting Error Sources by RF Band   Error Dependence on DOR Tone Frequency and Error Dependence on DOR Tone Frequency and  Structure Structure  Example: Example: MRO X/Ka Results MRO X/Ka Results   Proposed DOR Tone (Flexible) Specifications Proposed DOR Tone (Flexible) Specifications   Spectrum Management Issues Spectrum Management Issues   Ground Station Compatibility Issues Ground Station Compatibility Issues  J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 2 2 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Purpose Purpose  This This is not is not a request to revise CCSDS 401 a request to revise CCSDS 401  (2.5.6B) (i.e. DOR Tone Specification) (i.e. DOR Tone Specification) (2.5.6B)  The intended purpose The intended purpose is to continue a is to continue a  discussion within the DDOR SIG (WG) discussion within the DDOR SIG (WG) about whether we should request a about whether we should request a revision to CCSDS 401 (2.5.6B) CCSDS 401 (2.5.6B) revision to J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 3 3 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Delta Differential One-way Range Delta Differential One-way Range Spacecraft ∆ DOR complements line-of-sight DOR complements line-of-sight ∆   range and Doppler measurements range and Doppler measurements Quasar ∆ DOR uses interferometry to DOR uses interferometry to ∆   directly measure spacecraft angular directly measure spacecraft angular position in the radio reference frame position in the radio reference frame Accuracy of 2 nrad is being used Accuracy of 2 nrad is being used   spacecraft delay τ today to support targeting for Mars to support targeting for Mars today missions missions Tighter accuracy requirements may Tighter accuracy requirements may   θ be imposed by future missions be imposed by future missions The measurement is a group delay The measurement is a group delay  Correlator  Baseline B Measurement precision scales with Measurement precision scales with   signal spanned bandwidth signal spanned bandwidth τ = B ⋅ cos( θ )/ c τ J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 4 4 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Projected Navigation Requirements Projected Navigation Requirements  Navigation community has developed draft DSN Navigation community has developed draft DSN  tracking system requirements to support future tracking system requirements to support future mission set mission set  Year 2010: Year 2010: 2 nrad 2 nrad ∆ ∆ DOR accuracy DOR accuracy   To support Mars missions To support Mars missions   Requirement can Requirement can be met today using X-band be met today using X-band   Year 2020: 1 nrad Year 2020: 1 nrad ∆ ∆ DOR accuracy DOR accuracy   To support precise landing and/or sample return To support precise landing and/or sample return   Will be difficult using X-band Will be difficult using X-band   Year 2030: 0.5 nrad Year 2030: 0.5 nrad ∆ ∆ DOR accuracy DOR accuracy   To support precise landing and/or sample return To support precise landing and/or sample return   Need to use Ka-band Need to use Ka-band  J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 5 5 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology ∆ DOR Error Models DOR Error Models ∆  The accuracy of the measurement The accuracy of the measurement  τ τ S/C τ QSR1 τ QSR2 - ( τ + τ )/2 [for a QSQ sequence] S/C - ( QSR1 + QSR2 )/2 [for a QSQ sequence] depends on signal strength, spanned bandwidth, depends on signal strength, spanned bandwidth, receiver specifications, media calibrations, receiver specifications, media calibrations, baseline knowledge, … … baseline knowledge,  Equations have been developed to model Equations have been developed to model  measurement errors measurement errors  Limiting error sources have been identified Limiting error sources have been identified   Error budget has been developed and checked Error budget has been developed and checked  using data (X-band) from several missions using data (X-band) from several missions J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 6 6 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Limiting Error Sources by RF Band Limiting Error Sources by RF Band  S-Band S-Band   DOR Tone frequency DOR Tone frequency is 4 MHz is 4 MHz   Charged particles limit accuracy for most cases Charged particles limit accuracy for most cases   X-Band X-Band   DOR Tone frequency is 19 MHz DOR Tone frequency is 19 MHz   Limiting errors are spanned bandwidth (effect on precision and Limiting errors are spanned bandwidth (effect on precision and  instrument dispersion), charged particles, quasar structure instrument dispersion), charged particles, quasar structure • Charged particle errors reduced x13 relative to S-band (+) Charged particle errors reduced x13 relative to S-band (+) •  Ka-Band Ka-Band   DOR Tone frequency is DOR Tone frequency is 76 MHz 76 MHz   Limiting error is spanned bandwidth (effect on precision and Limiting error is spanned bandwidth (effect on precision and  instrument dispersion) instrument dispersion) • Charged particle errors reduced x15 relative to X-band (+) Charged particle errors reduced x15 relative to X-band (+) • • Quasar cores tend to be more compact relative to X-band (+) Quasar cores tend to be more compact relative to X-band (+) • • Quasar flux reduced Quasar flux reduced x(2-3) relative to X-band (-) x(2-3) relative to X-band (-) • • System temperature increased x(2-3) relative to X-band (-) • System temperature increased x(2-3) relative to X-band (-) J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 7 7 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Key Errors Scale with Spanned Key Errors Scale with Spanned Bandwidth Bandwidth  For a given phase measurement For a given phase measurement signal-to- signal-to-  noise ratio, delay error scales linearly with linearly with noise ratio, delay error scales (Spanned Bandwidth) -1 -1 (Spanned Bandwidth)  For a given instrumental dispersion (i.e. For a given instrumental dispersion (i.e.  bias) between spacecraft and quasar bias) between spacecraft and quasar phase measurements, delay error scales phase measurements, delay error scales linearly with (Spanned Bandwidth) -1 -1 linearly with (Spanned Bandwidth) J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 8 8 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Key ∆ ∆ DOR Error Terms at X-band DOR Error Terms at X-band Key and Ka-band and Ka-band  Precision of Precision of  (SNR) better than 1 better than 1 nrad at Ka nrad at Ka will require will require high high frequency frequency DOR tone DOR tone and high and high sample rate sample rate J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 9 9 J. S. Border CCSDS Meeting,

Jet Propulsion Laboratory California Institute of Technology Example: Dual Band X/Ka ∆ ∆ DOR DOR Example: Dual Band X/Ka Measurements of MRO Measurements of MRO  ∆ ∆ DOR measurements were made at both X- DOR measurements were made at both X-  band and Ka-band for 7 passes during MRO band and Ka-band for 7 passes during MRO cruise cruise  One pass (Jan. 20, 2006) included 40 One pass (Jan. 20, 2006) included 40 spacecraft spacecraft  and quasar observations and quasar observations  These data allow for direct comparison of X- These data allow for direct comparison of X-  band and Ka-band results band and Ka-band results  Ka-band spanned bandwidth was x4 and Ka- Ka-band spanned bandwidth was x4 and Ka-  band sample rate was x2 relative to X-band band sample rate was x2 relative to X-band J. S. Border CCSDS Meeting, Heppenheim Heppenheim, Germany, Oct. 2, 2007 - , Germany, Oct. 2, 2007 - 10 10 J. S. Border CCSDS Meeting,