1. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 Sprites observation by ISUAL on the ROCSAT-2 satellite J. L. Chern, R. R. Hsu, H. T. Su, A. B. Chen, and L. C. Lee Physics Department, National Cheng Kung University, Tainan 70101, Taiwan S. B. Mende Space Science Laboratory, University of California, Berkeley, CA 94720, USA H. Fukunishi and Y. Takahashi Geophysics Department, Tohoku University, Sendai 980-8578, Japan

2. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 The ROCSAT-2 satellite 891km altitude, sun-synchronized, polar-orbit, 9:30 am/pm at 23.5  N orbital plane: 98.99  period: 14 rev/day dry weight: 700kg (small-sat) pointing accuracy: ground error < 100m lifetime: 5 years payload: RS-camera, ISUAL launch day: 31 August, 2003

3. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 Major ISUAL science objectives To determine the location and timing of luminous phenomena above thunderclouds and to investigate their spatial, temporal and spectral properties to obtain an global survey of upper atmospheric optical flash transients (sprites, elves, blue jets etc.). To obtain an global survey of aurora and airglow

4. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Imager of Sprites / Upper Atmospheric Lightnings Instrument: a CCD Imager 6-channel spectrophotometer (SP) two array photometers (AP)

5. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL operation region 61.3deg ISUAL operation range (Not to scale) Earth 100km 17.8deg 891km Sun light

6. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL CCD Imager Limb-viewing Gated intensified CCD camera 512  128 pixel resolution 20 deg.  5.0 deg FOV (1173km x 150km at the 3373km) Burst or continuous modes (1 ms to 30 ms resolution) Six selectable filters

7. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Imager’s filters 1: 623 – 750 nm 2: 762 nm 3: 427.8 nm 4: 630 nm 5: 557.3 nm 6: Open (420-780 nm) wideband

8. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Imager filters Filter 1 N 2 1st positive band filter for observing Sprites. Removes the lightning induced 777.4 nm line and minimizes the airglow 760 nm O 2 band contribution. Filter 2 762 nm O2 (0,0) atmospheric band for observing airglow (waves) and aurora Filter 3 427.8 nm energetic electron induced emissions (sprites and aurora) Filter 4 630 nm auroral and airglow emissions Filter 5 557.7 nm auroral and airglow emissions Filter 6 Broad band filter (lens, no filter)

9. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL spectral photometers –Six photometer modules are identical except for spectral characteristics –20 deg.  5.0 deg. FOV –All boresighted in the same direction as the imager –All six channels are sampled at a 10 kHz rate

10. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Spectrophotometers - bandpass SP Channels 1&2 C1 - bandpass: 150 - 280 nm No filter used EMR type 541 PMT Rubidium Telluride photocathode Sapphire window C2 - bandpass: 250 - 390 nm Barr UG-5 glass filter EMR type 541 PMT Bi-alkali photocathode Magnesium Fluoride window

11. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Spectrophotometers - bandpass SP Channel 3&4 C3 - Center: 337 nm Barr interference filter EMR type 741 PMT Bi-alkali photocathode Sapphire window C4 - center: 391.8 nm Barr interference filter EMR type 741 PMT Bi-alkali photocathode Sapphire window

12. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Spectrophotometers - bandpass SP Channel 5&6 C5 - bandpass: 623 - 750 nm Barr interference filter EMR type 741 PMT Tri-alkali photocathode Sapphire window C6 - center: 777.4 nm Barr interference filter EMR type 741 PMT Tri-alkali photocathode Sapphire window

13. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Spectrophotometers - bandpass 1. Ultraviolet filter. Looking at N 2 LBH long wavelength bands. Upper state lifetime is 0.14 ms resulting in some quenching at lower altitudes. The altitude of unit optical depth is about 40 km in this range perhaps possible to see sprites while attenuating lightning. 2. Ultraviolet filter. It might be possible to see sprites and much attenuated lightning. 3. 337.0 nm N 2 2nd positive band requires higher electron energies therefore provides a particle energy “spectrometer”. 4. N 2 + 427.8 nm Energetic electron detector in sprites and aurora. 5. N 2 1st positive emission “bread and butter” sprite measurement. 6. 777.4 O lightning “perhaps trigger”.

14. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL Array Photometers Two 16-channel array photometers Red or blue filters Total FOV: 20 deg.  3.2 deg (20 deg.  0.2 deg each) Acquisition modes: –Sprite 1 mode: sampling at 20 kHz –Sprite 2 mode: sampling at 2 kHz –Auroral mode: sampling at 200 Hz

15. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL operation modes Sprite Continuous Mode –Imager is continuously taking images at a 100 frame/sec rate –Array Photometer is continuously sampled at a 20 or 2 kHz rate –Spectrophotometer is continuously sampled at a 10 kHz rate –All data are written into a series of circular memory buffers –Upon meeting trigger criteria on Spectrophotometer data, a selected block of data are saved in Mass Memory for compression and transfer to T/M –Selectable trigger parameters include channel, level, rise time, and pre-trigger block size and post-trigger block size Sprite Burst Mode –Same as continuous mode except sample rate is 650 Hz for a limited period –Price of high sample rate is ~80% dead time Auroral Mode –All instruments operate at a constant rate of 1 sample/second –All data saved, compressed, and transferred to S/C for downlink

16. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 Space/ground coordinated observations

17. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL contacts ISUAL Principal Investigater: Prof. Jyh-Long Chern (physics Dept., NCKU) jlchern@mail.ncku.edu.tw ISUAL NCKU Team: isual@phys.ncku.edu.tw UCB Team: mende@ssl.berkeley.edu Tohoku Team: fuku@pat.geophys.tohoku.ac.jp ISUAL website: http://sprite.phys.ncku.edu.tw/

18. NCKU UCB Tohoku ISUAL / ROCSAT-2 August 2001 ISUAL meetings During the 2001 AGU meeting at San Francisco an informal meeting Two days before the 2002 AGU meeting at San Francisco 2 days formal meeting at the Space Science Lab., UCB Additional information will be released on the ISUAL website.