current gbt performance

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

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

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

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