Inst. Overview Alice Preliminary Design Review JRS / 1 Instrument Overview and System Engineering John Scherrer (210) July 24, 2002

Inst. Overview Alice Preliminary Design Review JRS / 2 Topics Requirements Instrument overview S/C interface Rosetta Alice vs. New Horizons Alice Resources System Engineering Risk Management

Inst. Overview Alice Preliminary Design Review JRS / 3 Top Level Requirement The ALICE sensor shall obtain ultraviolet spectral maps over a 520 Å Å bandpass. The spectral resolution shall be 1.7 Å per spectral element. The FOV shall be 6° x 0.1º and the spatial resolution shall be 5 mrad/pixel. ALICE shall accommodate a solar occultation channel. * From section 3.3 of Mission Science Definition document

Inst. Overview Alice Preliminary Design Review JRS / 4 Flowdown of Requirements

Inst. Overview Alice Preliminary Design Review JRS / 5 General Description Alice is an integrated UV spectrograph composed of the following major elements: –A 41 x 65 mm off-axis paraboloidal primary telescope mirror. –A 50 x 50 mm toroidal holographic diffraction grating. –A 2-D imaging photon-counting microchannel plate (MCP) detector assembly with vacuum cover/window assembly. –Two entrance apertures: Airglow and Solar Occultation –Electronics that include: Microcontroller and C&DH electronics Double Delay line detector electronics Driver circuitry for actuators / heaters / switches, etc. Redundant high voltage power supplies Redundant low voltage power converters These elements are all packaged in a highly-baffled aluminum housing.

Inst. Overview Alice Preliminary Design Review JRS / 6 Mechanical Layout Detector Grating Zero Order Trap Solar Occultation Channel SOC Pick-off Mirror Baffles Aperture Opening OAP Mirror Slit Assembly Aperture Door (Shown Open)

Inst. Overview Alice Preliminary Design Review JRS / 7 Simplified Block Diagram

Inst. Overview Alice Preliminary Design Review JRS / 8 Optical Path Detector Grating Zero Order Trap Solar Occultation Channel (SOC) SOC Pick-off Mirror Baffles Aperture Opening OAP MirrorSlit Assembly Failsafe Door (Shown Closed) Aperture Door (Shown Open)

Inst. Overview Alice Preliminary Design Review JRS / 9 Rosetta Alice

Inst. Overview Alice Preliminary Design Review JRS / 10 Modes of Operation Histogram – builds up 1024 x 32 (spectral vs. spatial) array 16 bits deep. Primarily used for Airglow observations. Pixel List – Photon counting mode where the location of each photon event on the detector array (i.e. spectral and spatial location) is stored and transmitted. Time hacks are inserted to provide temporal resolution. This is primary mode of operation for Solar Occultation.

Inst. Overview Alice Preliminary Design Review JRS / 11 Interface Summary (1 of 2) Mechanical: –Hard mounted to S/C (or S/C bracket) –FOV is “aligned” with other optical instruments. Alignment: –Alice SOC shall be aligned to HGA (REX) within 0.23º (knowledge to 0.02º). Will use in-flight calibration to re-verify alignment. Thermal: –Desire to be at S/C temperature and coupled to S/C as much as possible (to minimize heater requirements). –Blankets cover most of exposed surfaces of Alice. (FOV’s are clear).

Inst. Overview Alice Preliminary Design Review JRS / 12 Interface Summary (2 of 2) Electrical: –Alice uses standard High Speed (LVDS) and Low Speed (UART) instrument interfaces. –Max telemetry rate is 480 kbits/sec (includes margin) which will occur during Solar Occultation (30 ksamples/sec). –Alice is equipped with SA 3865 microcontroller which allows for instrument flexibility and simplifies S/C interface. Microcontroller minimizes number of needed commands. Alice releases all doors via S/C telecommand Alice has internal autonomous safing functions (that can be disabled). Other: –Alice (as with all UV instruments) is contamination sensitive and will impose requirements on the spacecraft and other instruments. –GN2 (Grade C or %) purge through launch is required.

Inst. Overview Alice Preliminary Design Review JRS / 13 New Horizons Alice vs. Rosetta Alice (1 of 2) Environments: –NH is slightly wider temperature range. –NH is higher radiation environment. –Currently, NH loads are higher than as tested for on Rosetta. –Duration of the NH mission is longer though ON time is less. Optical: –Identical optics and detector –Slightly different bandpass required moving detector Electrical: –NH requires ping-pong memory. –For increased reliability, NH Alice has redundant LVPS and HVPS. –LVPS is custom design rather than hybrid. –Instrument controls actuators rather than spacecraft. –Different spacecraft interface.

Inst. Overview Alice Preliminary Design Review JRS / 14 New Horizons Alice vs. Rosetta Alice (2 of 2) Mechanical: –On NH, pyro’s are not allowed. Switched to wax pellet and shape memory alloy actuators. –Added Solar Occultation Channel aperture and pick off mirror. –Pump out tube length reduced. Thermal: –Very similar thermal design. Software: –NH is simpler spacecraft interface. –Simpler operations (reduced modes of operation and simpler requirements). Testing: –Very similar plan and series of tests.

Inst. Overview Alice Preliminary Design Review JRS / 15 Resources Mass: –Current Best Estimate = 3.86 kg –Mature value (with uncertainty 12.6%) = 4.35 kg –Values are known and approved by project. Power (data acquisition mode): –Current Best Estimate = 4.74 watts –Mature value (with uncertainty 15%) = 5.45 kg –Assumes 65% efficiency of LVPS –Current allocation is 5.64 watts TM Rate –Maximum expected rate is 480 kbps –This rate is based on highest expected count rate during Solar Occultation plus margin. –S/C capability on TM interface is 16 Mbps.

Inst. Overview Alice Preliminary Design Review JRS / 16 System Engineering Main responsibilities: –Verification of technical requirements DOORS, Verification Plan, Test Procedures –Management of technical resources Monthly reports –Oversight and control of system interfaces ICD’s, specs, Div. 15 Change Control process John Stone is lead of System Engineering –Dave Slater (Proj. Scientist), as well as PM and subsystem leads support SE activities.

Inst. Overview Alice Preliminary Design Review JRS / 17 Risk Management: Process We are transitioning to use of Web-based Risk Management Tracking System from more traditional spreadsheet system. –Similar to NAIMS (New Horizons Action Item Management System) –Automatically s responsible person for updating of status of risk item and mitigation plans. Risks ranked by Consequence and Likelihood. Mitigation Plans with trigger dates included. Team is polled weekly for their “worries”. Risks are statused monthly.

Inst. Overview Alice Preliminary Design Review JRS / 18 Top 5 Current Risks

Inst. Overview Alice Preliminary Design Review JRS / 19 Reynolds 600 HV Connector Discussion

Inst. Overview Alice Preliminary Design Review JRS / 20 Backup Material Alice Instrument Performance Specification (Draft) Mechanical Interface Control Drawing (Draft) Thermal Interface Control Drawing (Draft) Fault Tree Project Schedule Contamination Control Plan Verification Test Plan Radiometric Calibration Plan Software Development Plan Software Requirements Document (Draft) Preliminary Structural Analysis Preliminary Thermal Analysis