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Current GBT Performance. Systematic Focus Errors. Axial Focus Offset: air temperature versus elevation. Gravitational & Temperature Focus Effects. Temperature Effect. Gravitational Effect. Measure focus over short time period. NCP source 0117+8928. Systematic Pointing Errors. - PowerPoint PPT Presentation
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December 3/4, 2003 Green BankGBT PTCS In-Progress Review
Current GBT Performance
GBT PTCS In-Progress Review – December 3/4, 2003
Systematic Focus Errors
Axial Focus Offset: air temperature versus elevation
GBT PTCS In-Progress Review – December 3/4, 2003
Gravitational & Temperature Focus Effects
Temperature EffectGravitational Effect
Measure focus over short time period
NCP source 0117+8928
GBT PTCS In-Progress Review – December 3/4, 2003
Systematic Pointing Errors
GBT PTCS In-Progress Review – December 3/4, 2003
Plan of Attack
• Rationalize data acquisition
• Rationalize data analysis
• Implement temperature sensor system
• Concentrate efforts on pointing and focus
• Characterize performance with X-band (8 -10 GHz)
GBT PTCS In-Progress Review – December 3/4, 2003
Data Quality
Jack Scan
Gaussian Fits (Az, El, Focus)
Polarization (LCP – RCP)
Direction (Forward – Backward)
GBT PTCS In-Progress Review – December 3/4, 2003
Data Quality: Pointing (LCP – RCP)
GBT PTCS In-Progress Review – December 3/4, 2003
Data Quality: Pointing (LCP – RCP)
sec)(
2.0arc
JyS
Flux (9 GHz) > 0.08 Jy
RMS < 2.5 arcsec < 0.03 HPBW
GBT PTCS In-Progress Review – December 3/4, 2003
Data Quality: Focus (LCP – RCP)
mmJyS
)(
3.0
Flux (9 GHz) > 0.08 Jy
RMS < 3.8 mm << focus beamwidth
GBT PTCS In-Progress Review – December 3/4, 2003
Data Quality: Pointing (F – B)
sec1.068.0)( arcBF
sec1.054.0)( arcBF
GBT PTCS In-Progress Review – December 3/4, 2003
Data Quality: Wind
1''
12
2
11
68
2)(
sec16.0)(
smsat
windwind
arcsm
swind
GBT PTCS In-Progress Review – December 3/4, 2003
Observational Strategy
• NCP source to probe temperature effects
• Up-down sources at night to probe gravity effects
• All-sky for a combination
GBT PTCS In-Progress Review – December 3/4, 2003
Initial Results
• All-sky (Az, El) pointing– Removed systematic pointing residuals
• Simultaneous fits to gravity and temperature– Separate two effects– Refine focus and pointing models
GBT PTCS In-Progress Review – December 3/4, 2003
Current Performance
• Model: – Simultaneous solution to temperature and gravity effects
• Datasets: – All-sky pointing run (2003 Nov 20)– Half-power tracking (2003 Nov 20)
• Metrics– Blind pointing– Offset pointing– Continuous Tracking
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: Azimuth
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: Elevation
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Focus
GBT PTCS In-Progress Review – December 3/4, 2003
Offset Pointing: Azimuth and Elevation
GBT PTCS In-Progress Review – December 3/4, 2003
Offset Focus
GBT PTCS In-Progress Review – December 3/4, 2003
Tracking: Ku-band (14 GHz) El half-power track
sec12 arc
)/'10,/'2(,
)5,1(),(
)58,290(),(
mmt
El
t
Az
ElAz
ElAz
GBT PTCS In-Progress Review – December 3/4, 2003
Current Performance: (NO temperature corrections)
mmfocus
arc
5.2)(
sec52
mmfocus
arc
5.1)(
sec7.22
sec12 arc
Blind Pointing: (1 point/focus)
Offset Pointing: (90 min)
Continuous Tracking: (30 min)
Benign Conditions: (1) Exclude 10:00 18:00 (2) Wind < 2.5 m/s
GBT PTCS In-Progress Review – December 3/4, 2003
Supplemental Material
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Focus
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: residuals versus (A, Z)
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: residuals versus time
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: 2-D RMS
Raw Residuals
One PEAK at the start ofthe evening
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: Azimuth
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Pointing: Elevation
GBT PTCS In-Progress Review – December 3/4, 2003
Blind Focus
GBT PTCS In-Progress Review – December 3/4, 2003
Tracking: Ku-band (14 GHz) El half-power track
GBT PTCS In-Progress Review – December 3/4, 2003
Tracking: Ku-band (14 GHz) El half-power track