JANUS An Earth-Sun Observing L1 Mission

1. JANUS An Earth-Sun Observing L1 Mission JANUS Team Briefing to the ISAL & IMDC July 11th & 25th, 2005

2. JANUS IMDC Briefing Agenda • Team Introduction (Gerry Lead) • Science/Mission Overview (Jay/Joe Lead) • Instruments Overview (Jeff Lead) • Inter-instrument compatibility Issues • Prioritization & De-scopes • Operations Concept (Joe/Jay Lead) • Pointing Concept (Joe) • Pointing platform & guide telescope concept • Data Communications Concept (Jonathan Lead) • IMDC Trades (Dave Lead)

3. JANUS Mission Formulation Team Dr. Jay Herman Code 613 Lead Implementation PI & Earth Spectrometer lead Co-I Dr. Joe Davila Code 612 Lead Solar Instrument Suite Co-I Dr. Clarence Korendyke NRL Lead NRL Instruments Co_I Gerry Daelemans Code 462 Project Formulation/Capture Manager Jeffery Jones Code 556 Instrument Manager David Bundas Code 599 Missions Systems Lead Jonathan Gal-Edd Code 581 Data Communications Lead Eric Mentzell Code 551 Optics Design Lead Kate Hale Code 544 Electro-mechanical Lead Tropospheric nitrogen dioxide Solar Coronal Mass Ejection Dust Aerosols Airglow at 100 km Biomass Burning EUV Spectroscopy Ozone

4. JANUS – An Earth-Sun Mission at L1 Tropospheric nitrogen dioxide • Mission Description • Delta-2 launch vehicle to L1 Halo orbit • 3.5 month transit, 6 months to orbit • 3 year lifetime, 5 year goal • Daily science telemetry, and real-time, low-rate broadcast mode EUV Spectroscopy Airglow at 100 km • Technology Development • None required • Measurement Strategy • Continuous Earth and Sun viewing, and continuous upstream particle monitoring • Sun (EUV) and Earth (EUV, FUV, VIS, IR) spectroscopy to provide new physical understanding • Coronagraph and solar wind and energetic particle measurements provide continuous space weather information

5. JANUS Science Objectives • Understand the relationship between solar activity and the structure and dynamics of Earth’s atmosphere from the surface to the thermosphere-ionosphere for a range of seasons, solar radiation and energetic particle inputs. • Understand the role of plasma dynamics in coronal heating, solar wind acceleration, flares and transients, and UV irradiance variations. • Understand the role of transport and source distribution using high-resolution synoptic mapping of environmentally important species, tracking of pollution plumes, and ozone layer dynamics with the input to GCM chemistry models. • Provide real-time space weather data for predictive modeling of the space environment and Earth’s upper atmosphere. • Provide solar storm data for the purpose of protecting satellite communication, astronaut safety, ground power distribution assets.

6. Earth Viewing Spectrometers FUV, EUV (58 – 240 nm) UV-VIS, NIR (240 – 960 nm) (2 Telescopes with Multiple Focal Planes) Sun Viewing Package: Solar Coronagraph (Vis) Solar EUV Spectrometer Soft X-Ray Spectrometer Solar Wind Package Mag. Field+ Particles • JANUS has three suites of instruments to accomplish JANUS Science Objectives: • - 2 Earth Viewing Spectrometers • 240 – 960 nm 0.5 meter mirror Near-UV, VIS, Near-IR • 85 – 240 nm 16 cm mirror EUV and UV • - A Solar Viewing Suite of Instruments • NEXUS EUV Spectrometer • Coronagraph • Irradiance Monitor (Soft Xray Spectrometer? • - An in-situ Suite of Instruments • Magnetometer • Solar Particle Counter

7. JANUS System Block Diagram Solar Guide Telescope Solar Instrument Suite (SIS) Earth Instrument Suite (EIS) Error signal Error signal S/C Bus NEXUS EUV Spectrometer Visible Light Spectrograph 0.5 m Telescope White Light Coronagraph EUV/FUV Spectrograph 0.16 m Telescope Irradiance Monitor SIS MEB EIS MEB Internal EIS,SIS Data Bus’s S/C to EIS,SIS Data Bus Solar Wind In Situ Instrument Suite (SWIS) SIS Mech Drive Elect. EIS Mech. Drive Elect. S/C to EIS,SIS Power Solar Wind Particle Counter High Gain Antenna Boom Magnetometer

8. Earth Viewing Instrument Descriptions • Spectrometer with 0.5 meter primary mirror Cassegrain operating in two focal planes. The secondary mirror is active for scanning and jitter control. • a. 240 to 500 nm with 1 nm resolution from 300 to 500 nm • b. 480 to 960 nm with 4 nm resolution from 480 to 960 nm • There are 10 narrow wavebands from 240 to 300 nm • Uses beam-splitter onto two separate slits, gratings, and detectors. • Uses flat folding mirrors and flat gratings. • Uses concave mirror for focusing • High data rate of 2.5 Mbps 24/7 • Signal to Noise required of 500:1 for spatial resolution of 6 km nadir • Requires image stabilization to 1/3 pixel (0.25 arcseconds) • 2. Two NEXUS-style Spectrometers for EUV and short-wavelength UV • Uses ~16 cm primary and torroidal grating for minimum number of reflecting surfaces. • No image stabilization needed because of coarse spatial resolution ~10 arc seconds (100 km) • Uses xxxxx pixel detector

9. Instrument Overview • Jeff: Please create the necessary charts to orient the IMDC on the instruments mentioned in the previous slide. • Take into account Compatibility issues between instruments that don’t come across from the data we supplied via the IMDC Web site • Discuss the prioritization and descope sequence

10. JANUS Operations Concept • Insert into 700 km LEO for 1 or 2 orbits • Perform Basic Checkout (Low Power) • Launch towards L-1 • Deploy Solar Panels • Check Main Transmitter (High Power) • Perform Full checkout (High Power) • After 1 to 2 weeks Start Earth-Instrument Operations • Start solar instruments - Checkout • When the spacecraft is more than 15 degrees from the Earth-Sun line, point the spacecraft at the sun to obtain only solar data for the next few months. • Assuming we have the 18-meter Ka-band antenna, start ground-system operations at 2 hours per day to receive solar data • Start Earth-Sun operations at the 5 to 6 month period when within 15 degrees of L-1 • Ground systems operation increased to 4 hours per day • Once L-1 orbit is stabilized, full Earth-Sun operation with data 24/7 requiring 4 hours of ground data reception.

11. JANUS Earth-Viewing Spectrometer Operations • Average Exposure Time 0.1 sec • CCD Readout 0.1 sec • 4 exposures per line co-added onboard the spacecraft (2048x2048 pixels) • Raster mirror moves 0.75 arcseconds in object space. • Repeats 4-exposure cycle • Raster mirror moves ~2000 times to cover the entire Earth disk. Image Stabilization • Raster mirror also moves in 2-d to stabilize the image • Stabilization information comes from a guide telescope focused on the Sun’s limb • Stabilization to 1/3 pixel or 0.25 arcseconds in object space • Motions in object space are about 1/3 the motions in image space Multi-Scan Earth View 2,000 raster lines 2048 pixels 2048 pixels Wavelength CCD 2048 pixels Spatial

12. JANUS Pointing Concept • Joe, please provide what is necessary to orient the IMDC folks around our baseline pointing platform scenario,& some more detail about our use of the guidetelescope to handle fine pointing/de-jitter, etc.

13. JANUS Trades • Dave, Joe Jay,,,,do we have any trades we want the IMDC to look at?

14. JANUS Data Communications Concept • Assumptions for Earth-Viewing Spectrometer 240 to 960 nm: • Assume the use of a 2k x 2k detector • Assume a total wavelength range from 250 to 960 nm • Assume: 300 to 500 nm at 1 nm resolution = 200 elements • 500 to 906 nm at 4 nm resolution = 120 elements • 250 to 300 nm 10 narrow bands = 10 elements • Total data elements 2000 x 330 = 6.6x105 elements • Assume 16 bits per element => 1.06x107 bits per spatial line • Exposure time and readout is about 1.1seconds (~0.6 hours per full globe) • This yields a data rate of 9.6x106 bits per second uncompressed • or 4.8x106 bps compressed. • 10. Measurements only once per hour (*0.61) = 2.9x106 bps • Only illuminated pixels (*0.79 = pi/4) = 2.3x106 bps • 11. We need approximately 2.5 Mbps for the range 250 to 960 nm • 12. Estimated Ka band rate is 64 Mbps. Using a 4-hour downlink, this is • equivalent to about 10 Mbps continuous data acquisition. • 13. The remainder 7.5 Mbps is available for the solar instruments and the Earth-viewing EUV instrument