System Performance Metrics and Current Performance Status

George Angeli

Performance Metrics

Image Quality

Image DepthPhotometric Repatability

Astrometric Repeatability

Ellipticity

Image Quality

Throughput

Read Noise

Integrated Étendue

Fill Factor (fF)

Observing Efficiency (fO)

Technical Performance Measures

Measures of Performance:

SRD Data Properties

Measures of Effectiveness

*

Calibration update in-progress

Updated estimates

Integrated Étendue

− Basic definition

− Extended definition• Sensitivity• Integrated étendue

- Fill Factor (fF ) - accounts for losses in the field due to masks, bad pixels, charge stops

- Sensitivity Factor (fS ) – accounts for sensitivity losses or gains due to throughput, image quality, read noise

- Observing Efficiency Factor (fO ) – accounts for losses or gains in open shutter efficiency over the entire survey

FieldOfView CollectionArea OpenShutterTime

real P nom F nom S nom O nom

E

E f E f FOV f CA f OST

55

1S CAt

real F nom S nom O nom

P F S O

E f FOV f S f OST

f f f f

Sensitivity Factor• Not allocated - driven by allocable Technical Performance Metrics:

– Image Quality– Throughput– Read noise

• For each band:

• Overall fs as time weighted sum

Observing band (filter) Time Allocation

e2v mAR Depth

Margin over SRD Des. fS

u band 6.7 % 23.7 - 0.184 0.712

g band 9.7 % 24.9 - 0.064 0.888

r band 22.3 % 24.5 - 0.242 0.641

i band 22.3 % 24.0 - 0.001 0.997

z band 19.4 % 23.4 0.149 1.317

y band 19.4 % 22.5 0.433 2.219

Overall 1.185

margin 10 101.25 log 1.25 logrealS

nom

tm f

t

Evolution of Image Depth ReserveReserve in LSR above SRD Minimum Specification

See Chuck’s presentation for details

Sensitivity factor relative to SRD minimum specs:

1.69 1.83

FDR LSST20140.000

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450

u bandg bandr bandi bandz bandy band

Imag

e De

pth

Rese

rve

abov

e SR

D M

in-

imum

[m

ag]

P R O P O S E D

Image Depth Dependencies

• For each band:Image QualityThroughput and read noise

2

5 101.25 log 0.69 0.310.4mm C

350 360 370 380 390 400 410 420 430 440 450

-50

-40

-30

-20

-10

0

10

20

30

40

50

Image quality [mas]

5 [

]Dm

mmag

7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0

-60

-40

-20

0

20

40

60

Read noise [e-]

5 [

] Dm

mmag

r band

Change since JIM Review

Image Quality Error Budget

Optical designM1M3 shape

M2 shapeTelescope collimation

Active opticsTelescope dynamicCamera optical fab.

Camera assemblyCamera gravity

Camera thermalCamera pressureCamera vibration

Camera sensor flatnessCamera raft height

Camera cryostat heightCamera charge diff.

Total system reserve

0 50 100 150 200 250

milliarcsecond (mas)

Telescope reserve: 105 masCamera reserve: 102 mas

See Bo’s presentation for details of meeting this budget

Evolution of IQ System Reserve

Charge diffusion contribution estimate reduced before FDR from 259 mas to 186 mas

milliarcsecond (mas)

PDR JIM FDR LSST20140

50

100

150

200

250

Optical System

Structural System

Detector

Atmosphere

Sky Objects

Optics position & shapeTe

mpe

ratu

re,

Tem

pera

ture

gra

dien

ts,

Tele

scop

e el

evati

on,

Air p

ress

ure

ControllerA

Actuators

Supe

rvis

ory

cont

rol,

Tele

scop

e el

evati

on

TCS

Temperature

Force balance

WF & State Estimator WF & Guider Data

ControllerB

Temperature

System Behavior

PSF size and shape

Integrated System Model

Optical Kernel

TelescopeStructural

ModelImage Metrics

Tem

pera

ture

, Te

mpe

ratu

re g

radi

ents

, Te

lesc

ope

elev

ation

,Ai

r pre

ssur

e

ControllerA

Actuators

WF & State Estimator

WF & Guider Data

Camera optics position & shape

Camera Structural

Model

Detector temperature

Tem

pera

ture

, Te

mpe

ratu

re g

radi

ents

, Te

lesc

ope

elev

ation

PSF size and shape

Currently ZEMAXPreferably PhoSim

• Deterministic effects– Optical design residual errors, – Diffraction effects due to the finite aperture and pupil obscuration,

• Deterministic effects randomized by environmental and operational parameters– Mirror support print through and lens gravitational deformations randomized

through telescope zenith angle– Thermal deformations of optical surfaces and support structures randomized

through ambient and local temperature• Random processes

– Dome and mirror seeing– Local actuator and sensor noise and drift (non-optical sensors)– Counting statistics– CCD sensor effects (solid state effects: diffusion, field dependencies, penetration

depth, QE variations)– WFS measurement, estimation, and control errors– Material, fabrication, and installation errors; these become deterministic once

the “as built” system is available

Input Parameters (Perturbations)

• FWHM across the field• Ellipticity across the field

Output Parameters (Metrics)

• Area weighted mean of 31 samples– Diffraction (FFT) PSF– Also track geometric PSF

derived from spot RMS

• Fiducial atmospheres (3) – Scaled to 0.44”, 0.6”, and 0.8” FWHM seeing on the aperture of

LSST.• • Zenith angle range of 0˚- 65˚

– Statistical distribution derived from “standard” OpSim simulations.

• Temperature and pressure ranges as defined in the OSS as Normal Operating Conditions. – The temperature inside enclosed volumes, like the Camera, needs

to be estimated from these environmental parameters.

• The expected temperature range of the detector, with assumed statistics

Environmental Conditions

• Transition the optical kernel to PhoSim

• Include missing instrumental perturbations– Most prominently sensor effects– In the process of implemented in PhoSim

• Improve AOS control laws and performance

• Establish a configuration adequate for science simulations– Linked or emulated AOS

Future Work