Design Review Spartan IR Camera
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Design Review Spartan IR Camera E Loh, Physics-Astronomy Department, Michigan State University East Lansing, 22 May 2001. Science Goals (ref: NSF proposal) Optical Design (ref. “Optical Design”) Optical alignment (ref: “Alignment” & “SOBER”) System Design & Electronics (ref. “Electronics”)

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Science Goals (ref: NSF proposal) Optical Design (ref. “Optical Design”)

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Science goals ref nsf proposal optical design ref optical design

Design Review Spartan IR CameraE Loh, Physics-Astronomy Department, Michigan State University East Lansing, 22 May 2001

Science Goals (ref: NSF proposal)

Optical Design (ref. “Optical Design”)

Optical alignment (ref: “Alignment” & “SOBER”)

System Design & Electronics (ref. “Electronics”)

Mechanical Design (ref. “Mechanical Design”)

Budget & Schedule (ref. “Budget & Schedule”)


The team

The Team

  • Jason Biel, technician

    • Measurements for vacuum design

    • Electronics designer & technician

  • Mike Davis, graduate student

    • Optics

  • Owen Loh, Okemos High, volunteer

    • Finite-element analysis

    • Drafting

  • Tom Palazzolo, head, Phys-Ast shop

    • Mechanical shop, design advice, contact for mechanical designers & job shops

  • Jack Baldwin, Brooke Gregory, Ron Probst, Dan Edmunds, Phys-Ast EE, advisors

  • E Loh

DR SOAR Spartan IR Camera


1 science goals

1. Science Goals

Tip-tilt corrected imaging in the J, H, & K bands

  • To cover the wide, corrected field (5’)

  • To resolve FWHM of median seeing (0.15–-0.23”)

  • To resolve high-contrast features at the diffraction limit

    (0.08” @H & 0.11” @K)

DR SOAR Spartan IR Camera


Point spread function with tip tilt correction

Point-spread Function with Tip-Tilt Correction

  • Point spread function is not a gaussian

  • Diffraction spike

Top quartile

Median seeing

DR SOAR Spartan IR Camera


Image width

Image Width

  • Sub 0.5” images w/o tip-tilt

  • 0.15-0.23” images w tip-tilt

  • Telescope optics preserves images

Telescope degradation. Goodyear CDR

DR SOAR Spartan IR Camera


2 optical design

2. Optical Design

  • Concept

  • Image Quality

  • Tolerances

DR SOAR Spartan IR Camera


Optical concept

Optical Concept

  • Requirements

    • Large number of pixels [ 2 x 5’ / 0.08” = 7500 pixels ]

    • Large telescope image [ 5’ x 4.2m x 16 = 100mm square]

  • Rockwell 2048x2048 HgCdTe detector

    • 4 detectors & 7500 pixels  two plate scales

  • Reflective optics  large telescope image

  • Off-axis collimator & camera mirror

    • Parent design: two paraboloids

      • Perfect image for 1:1 & small field

    • Real design for change in plate scale

      • Adjust conic constants, distances

      • Field flattening lens

DR SOAR Spartan IR Camera


Design

Design

  • Four 20482 detectors

  • Two plate scales: 0.08 & 0.04”/pixel

  • 20 filters near pupil

  • Focal plane mask

    • coronagraphy

    • spectroscopy

DR SOAR Spartan IR Camera


Image quality spot diagram

Image Quality: Spot Diagram

  • 9 Field points in a grid. Corners are corners of 4 detectors.

  • H band

Airy disk

f/11

f/21

DR SOAR Spartan IR Camera


Image quality strehl ratio

Image Quality: Strehl Ratio

  • 9 Field points in a grid. Corners are corners of 4 detectors.

  • Strehl is very high for diffraction sampled cases, f/21 in H and K bands

Sampled for diffraction limit

DR SOAR Spartan IR Camera


Tolerances

Tolerances

  • Error budget

    • Loss of Strehl of ~0.07mag

  • Alignment

  • Manufacturing

DR SOAR Spartan IR Camera


Alignment tolerances

Alignment Tolerances

6mil

1mil over 6in

DR SOAR Spartan IR Camera


Manufacturing tolerances

Focal lengths are absorbed in focus

SORL can manufacture conic constants

Surface irregularity

Peak-to-valley is l/16 to l/4.

l = 633nm

Manufacturing Tolerances

DR SOAR Spartan IR Camera


Alignment with sober

Align at room temperature with point source, SOBER, & CCD

SOBER

f/16 beam

Move SOBER & shift stop to mimic pupil at 10m

z stage mimics curved focal surface of telescope

Tolerances 1mm & 1º

Image in IR? TBD

Alignment with SOBER

LED & pinhole

Lenses

z stage

Sliding stop

R- stage

ISB surface

Soar Beam Simulator

DR SOAR Spartan IR Camera


Alignment indicator

Intensity of 9 field points indicates error

Alignment Indicator

Y-decenter of collimator 0.34mm

X-tilt of fold #1 of 0.2mrad

DR SOAR Spartan IR Camera


Test of alignment

Test of Alignment

Defect: I7<I9

x-position of collimator; wrong

y-tilt of lens; right

Defect: I5<I8

x-tilt of fold #1

DR SOAR Spartan IR Camera


3 system design electronics

3. System Design & Electronics

  • System

  • Electronics

  • Software

  • Motors

  • Vacuum

DR SOAR Spartan IR Camera


System design

System Design

Legend

Camera Controller

Detector

Fiber optic

In control rack

Camera Controller

Camera Controller

Detector

PC

Camera Controller

Detector

Umbilical

NI 6533

Camera Controller

Detector

RS232

RS232

Stages

Motor Controller

DeviceNet

RS232

Pressure Sensor

In vacuum

On camera

Ethernet

Custom

Observer

Data Archive

Telescope Control

Elsewhere

Commercial

DR SOAR Spartan IR Camera


Umbilical card

Umbilical Card

Camera card

One of 4 channels shown

  • Provenance

    • CCD system

Fiber-optic

tranceiver

Master clock

Logic Analyzer

Serializer

deserializer

Test pod

For debugging

Existing CCD Software

on Alpha

FIFO

NI 6533 interface

DRV11 interface

In FPGA

NI 6533

Laptop-type power supply

DR SOAR Spartan IR Camera


Camera card

Camera Card

  • Provenance: CCD camera

  • 4 analog channels for 4 quadrants

Timer &

clock generator

Buffer

Logic Analyzer

Amplifier &16-bit ADC

(2 12-bit ADC)

Instruction

Test pod

Detector

Laptop-type

power supply

Fixed voltages

(digital pot)

Serializer

deserializer

In FPGA

Diodes

Temperature

Fiber-optic

tranceiver

Phase-locked

loop

Umbilical card

DR SOAR Spartan IR Camera


Umbilical card1

Umbilical Card

  • 3U 100160 mm

  • Tested w/ CCD software

To existing computer

Fiber optic

to 4 detectors

NI 6533

FPGA

7V in

160mm

To logic analyzer

DR SOAR Spartan IR Camera


Camera card1

Camera Card

  • 3U 100160 mm

  • Low crosstalk

    • 5-mil between signal & ground layers

  • Delivery expected in 2 weeks

  • 2.5ms/pixel

  • 4 channels

  • Power: 1.4W

7V in

Signal chains

Fiber optic

Flex cables to detector

Neck between

analog & digital circuits

FPGA

DR SOAR Spartan IR Camera


Noise

Noise

  • Detector noise is about 10e–; noise on amplifier glow is 5e–.

  • Electronics noise is 6e–.

  • Coupling from a saturated channel is about 2e–.

  • Coupling from clocks on cable is large.

    • Sampling signal must wait 100ns after clock transition.

DR SOAR Spartan IR Camera


Detector card

Detector Card

  • Card butts on 2 sides

  • Connects to camera card with 5 flex cables, which are thermal resistors.

  • 3 layers with 5-mil G10.

Flex cables

Electrically isolated straps

to nitrogen dewar

ZIF socket

Detector

DR SOAR Spartan IR Camera


Software

Software

  • Functions [copied from Optical Imager]

    • Control detector

    • Scripting

    • Communicate with motors

    • Communicate with telescope control system

    • Communicate with user

  • ArcView

    • Used for all SOAR instruments

    • CTIO will debug ArcView with Optical Imager, the commissioning instrument

  • LabView, “visual programming”

    • Independent of hardware  obsolescence is obsolete

    • Self documenting

    • Easy to do. ArcView costs < 1 man-year

DR SOAR Spartan IR Camera


Software tasks

Software Tasks

  • Design

    • Use commercial parts with LabView drivers

  • Modify ArcView

    • Computer send commands and receives data from camera controller through NI 6533 card.

      • Replace Leach controller & driver with NI 6533 card.

      • Our card has a 4k sample FIFO

        • 0.6ms margin for 4 detectors reading simultaneously

    • Write software for summing pictures

    • Change software for formatting picture

    • Change motor controls

    • Add temperature & vacuum sensing

DR SOAR Spartan IR Camera


Motion

Motion

  • Phytron stages DT-90 & MT-85

    • Vacuum compatible

    • Stepper motor

    • Indexing switch

    • Limit switches

    • Open loop; controller stores position

  • Controller

    • RS232 to computer

    • LabView

    • Heat

      • Shutoff power? Cooler?

DR SOAR Spartan IR Camera


Vacuum measurement

Vacuum Measurement

  • Granville-Phillips ion gauge

    • Computer readout via DeviceNet

    • LabView

    • 12W; need to shut off

DR SOAR Spartan IR Camera


4 mechanical design

4 Mechanical Design

  • Cryogenic optical box

    • A-frame attachment to vacuum enclosure

    • Analysis of flexure

  • Vacuum enclosure

    • Analysis of stress

    • Transfer of forces from A-frame to instrument mounting box (ISB)

  • Mechanisms using warm stages

    • Layout

    • Proof of concept

      • Flexure

      • Heat load

      • Operating temperature of stage & optics

DR SOAR Spartan IR Camera


Cryogenic optical box

Cryogenic Optical Box

  • Symmetric box having two plates equidistant from optics.

    • Gravity vector is in plane.

    • Optics supported by both plates.

      • Torque perpendicular to plates

  • Box is attached near focal surface of telescope

    • Rotation of optical box causes no boresight error.

DR SOAR Spartan IR Camera


A frame attachment

A-frame Attachment

  • Connect cold optical box to warm vacuum enclosure

  • Complies with shrinkage of optical box

    • Web weak in z

  • Hold box w/o sag

    • Web strong in x & y

  • Heat load is 0.7 W for 4 A-frames.

Weak

for thermal compliance

Strongest; max sag:

14m or 0.04”

Al leg

G10 web

G10 ring

Section removed

for clarity

Bolt to

optical box

Bolt to warm

vacuum enclosure

Safety stop

DR SOAR Spartan IR Camera


Rotation of optical box

Rotation of Optical Box

  • Gravity parallel to mounting plate. (Causes boresight error)

  • First approximation

    • Optical box rotates 40mrad as a unit

    • Sag is 14m at telescope focus.

  • More precisely

    • Error is greater for gravity perpendicular to mounting plate.

    • Rotation within box is 2.3mrad peak-to-peak

    • Boresight shifts 0.007”.

0–155mrad

34–46mrad

DR SOAR Spartan IR Camera


Vacuum enclosure

Vacuum Enclosure

  • Aluminum plate, mostly 1/2”

  • Max stress is here

    • Max is tensile strength / 2.2.

    • Code for pressure vessels is 3.5.

    • Is this OK?

DR SOAR Spartan IR Camera


Transfer of forces to bolts on isb

Transfer of Forces to Bolts on ISB

  • Does the vacuum enclosure transfer forces between the A-frames and the bolts on the instrument mounting box (ISB) without sag? Yes. Sag is 2m.

Optical box

Bolts to

A-frames

Bolts to ISB

Sides of vacuum enclosure

DR SOAR Spartan IR Camera


Mechanisms

Mechanisms

  • Two filter wheels

    • Loose tolerances

  • Focal-plane mask

    • 300m along optic axis, 18m in transverse direction

  • Collimator insertion

    • Tilt 5mrad (1”) as instrument turns for boresight with tip-tilt sensor

  • Camera mirror insertion

    • Tilt 5mrad as instrument turns

  • Rotate lens-detector by 112.7±0.6mrad

    • Tilt 0.2mrad (30m over 150mm)

  • Move lens-detector assembly for focusing

Difficult

DR SOAR Spartan IR Camera


Layout of mask filter wheel

Layout of Mask & Filter Wheel

  • Load is balanced  Easy to meet tolerances.

  • Phytron DT-90 rotational stages

    • Integrated stepper motor, indexing switch, limit switch

    • Spring constant 2mrad/(N-m). Wobble is ±15mrad (Clarification needed.)

Optical box

Rotation stage

Vacuum enclosure

Mask wheel

Filter wheel

DR SOAR Spartan IR Camera


Layout of mirror insertion

Layout of Mirror Insertion

  • Mirrors must be balanced to meet 5mrad tolerance.

Vacuum enclosure

Rotation stage

Mirror

Optical box

Counterweight

Background mirror

f/21 collimator

f/11 camera

DR SOAR Spartan IR Camera


Proof of concept insert f 21 mirror

Proof of Concept: Insert f/21 Mirror

  • Requirements. Cold mirror — warm stage — cold optical box

    • Support with tilt < 5mrad

    • Keep mirror cold

    • Keep stage warm

    • Minimize heat load

    • Comply with thermal expansion

  • Precepts

    • Balance load

    • Use G10 A-frames to control conduction & comply with thermal expansion

    • Shield stage from cold to control radiation

    • Allow stage to absorb radiation from warm vacuum enclosure

DR SOAR Spartan IR Camera


Mirror insertion

Mirror Insertion

4 A-frames

f/21 collimator

Center mass

Counterweight

DT90 rotational stage

4 A-frames between

stage & bracket (hidden)

Bracket attaches

to optical box

DR SOAR Spartan IR Camera


Results for f 21 insertion

Results for f/21 Insertion

  • A-frames have 1x1x5mm legs.

  • Balance within 1mm.

  • Wrap stage in 10 layers of aluminized mylar.

  • Results

    • Conduction is 170mW

    • Tilt is 2mrad; tolerance for boresight alignment is 5mrad.

    • Sag with mirror vertical is 8m; tolerance for internal alignment is 0.8mm.

    • Sag with mirror horizontal is 4m; tolerance for focus is 15m.

    • Temperature of mirror is 88K.

    • Temperature of stage is 2K below ambient. (Area of radiator is 10% that of the stage.)

DR SOAR Spartan IR Camera


5 budget schedule

5 Budget & Schedule

  • Budget

  • Contingency

  • Descope

  • Risk to budget

  • Schedule

DR SOAR Spartan IR Camera


Budget

Budget

  • Not allocated or charged: Majority of electrical engineer, mechanical engineer, project management, drafting (done so far), and finite-element analysis.

DR SOAR Spartan IR Camera


Contingency vs remaining tasks

Contingency vs Remaining Tasks

  • Tracking of tasks since budget of Aug 2000

    • Electronics design is 17% over budget. ($5k of $29k)

    • Design of telescope simulator is 65% over budget. ($5k of $8k)

    • Optics design is 31% under budget. ($6k of $19k)

    • Overall budget dropped $100k because mechanical design firmed up, optics shortened, and mirror quotes dropped.

  • Contingency is 36% of remaining tasks.

DR SOAR Spartan IR Camera


Descope

Descope

  • Descope 2nd plate scale, J, H, K, Ks filters only, spectroscopy & coronagraphy.

  • Descope will be treated as contingency.

    • Descoped items will be added as contingency allows.

    • Possible formula: spend if

      Budgeted Contingency > 1.5 Actual Contingency

DR SOAR Spartan IR Camera


Risk to project

Risk to Project

  • Number of risks covered

    • A big item is $100k.

    • Labor for optical box, mechanisms, enclosure is $70k with $30k contingency

      • Drafting: 3 mo.

      • Internal shop: 7 mo.

      • External shop: 1 mo.

      • Technician: 6 mo.

    • Contingency, $193k, covers 2 big risks

    • Descope, $175k, covers 2 big risks.

  • Descope & contingency  remaining tasks of descoped instrument

DR SOAR Spartan IR Camera


Schedule overview

Schedule Overview

DR SOAR Spartan IR Camera


Detector

Detector

  • Multiplexer & engineering-grade device delivered.

  • Long slack time before science-grade detector is needed.

DR SOAR Spartan IR Camera


Electronics

Electronics

  • 7 mo. slack

DR SOAR Spartan IR Camera


Optical box enclosure mechanisms

Optical Box, Enclosure, & Mechanisms

  • Optical box & enclosure will soon be a critical task.

  • Plans for mechanisms have changed.

    • Swales Aerospace’s estimate is 3 times higher than that of 1998.

    • New plan is to purchase high quality, warm stages & design non-precision parts.

    • Short slack.

DR SOAR Spartan IR Camera


Optics

Optics

  • Optics & filters are behind schedule.

    • Estimated time is 2–3 times longer than vendors’ quotes of 26 weeks, because of word-of-mouth tales.

    • Schedule could be made up with immediate requisitions and on-time deliveries

DR SOAR Spartan IR Camera


Software1

Software

  • ArcView will be fully tested by CTIO with the Optical Imager.

  • Scope of software task is uncertain.

    • No experience with LabView.

    • Need to see ArcView.

  • If task is beyond students’ capability, we will seek vendor such as Imaginetics.

DR SOAR Spartan IR Camera


Integration installation

Integration & Installation

  • There is a 16 week period for fixing problems.

  • Delivery is scheduled for 3/28/03.

DR SOAR Spartan IR Camera


Risk to schedule

Risk to Schedule

  • Tasks on the critical path

    • Optics are delayed.

    • Optical box & enclosure have little slack.

    • Mechanisms have a short slack.

  • Delay of funding is the greatest risk.

    • Without starting on the critical tasks, we cannot test our estimates. We cannot set accurate bounds on the task.

DR SOAR Spartan IR Camera


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