- Email: [email protected]
The flare genesis project
Adv. Space Res. Vol. 14, No. 2, pp. (2)89-(2)93, 1994
0273-1177/94 $6.00 + 0.00 Copyright © 1993 COSPAR
Printed in Great Britain. All rights reserved.
THE FLARE GENESIS PROJECT D. M. Rust The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, U.S.A.
ABSTRACT The feasibility of a balloon-borne experiment to understand how the magnetic fields at the solar surface emerge, coalesce, unravel and erupt in solar flares was studied. A key component of the Flare Genesis instrument will be a solar telescope with an 0.8-meter-diameter lightweight mirror. Effects of pendulation and jitter, gravity and temperature on the images formed by the telescope were studied to determine whether it will maintain the desired resolution of ~ 0.2 sec of arc at float altitude. The principal conclusions of the study are that (1) sufficient image stability can be maintained at the focal plane; (2) polarization sensitivity of 2 x 10-4 is achievable; and (3) the data system can store ~ 2000 magnetograms on-board in the course of a llYto-14-day Antarctic flight. INTRODUCTION All solar activity arises from the action of magnetic fields. Precise measurements of these fields will be essential for a complete description of the storage, release, and transport of energy in solar flares and other solar activity. The ground-based APL vector magnetograph /1,2/ has confirmed earlier evidence that measurable magnetic field changes probably trigger solar flares/3/. Further observations will doubtless yield added insights, but the potential of ground-based instruments for probing fundamental flare physics is severely limited by turbulence in Earth's atmosphere. We believe that the needed solar observations can be obtained economically in the Antarctic with a balloonborne solar vector magnetograph (SVMG) that can resolve the emerging flux and allow precise correlation of flux changes with flares. The magnetic sensitivity should be sufficient to reveal small changes as fields emerge, submerge or cancel. The SVMG, with 1024 x 2048 0.1"-pixels should lower the 3-o limit for detection of free energy conversion. We estimate the limit at < 1029 ergs over the 1.7'x 3.4' field of view. Many flares with magnetic energy consumption above this level should occur in a two-week balloon flight. INSTRUMENT OVERVIEW Figures 1 and 2 show the focal-plane components of the SVMG. The telescope (not shown) is an F/1.5 Cassegrain with a lightweighted 80-era Zerodur primary mirror and an articulated secondary mirror which produces an F/25 image near the entrance to the polarization module. For thermal control, the primary mirror surface will be overeoated silver or aluminum, which offer at least 95% refiectivity at the operating wavelengths and reduce the thermal loading on the mirror to less than 30 W. The secondary mirror will be transparent except for a narrow spectral band near 630 rim, so most of the 500 watts of collected solar energy will pass through it and exit the telescope. The solar vector magnetic field will be inferred from narrow-band filtergrams obtained at six sequential settings of the polaroids and quarter-waveplate in the Polarization Analysis Module (Figure 2). The filtergrams will correspond to measurements of the Stokes parameters: I + Q, I - Q, 1 + U, I - U, I + v and I - V. /4/. Each six-image sequence, obtained in 8 s, will constitute one vector magnetogram. The random motions of flux tubes on the Sun will limit the time that can be spent accumulating images for each Stokes parameter without loss of resolution. Since a typical flux tube will cross one 0.1" pixel in - 140 s, only seventeen sequences can be averaged together without anyloss in resolution.
JA~q i4:2-6
(2)89
(2)90
D.M. Rust
II 0.12 A Eudon Filter at pupil image ~
I I I I
1.5 A Blocltea"Filta" --._
/ ~
CCD Camera
~
CCD Camera Le~s I~1
Motion
Collimator ~
l
/ --
Field Lens
Hlte~ 200 A passband @ 63oo A
ensor
Microscope Objective
Anermaing7/4P,~eandwindow Rotating polaroid and Z/2 plate
~
Relay Lens
Image Rotator - Pechm Prism
Tilt ~ Mirror
[
image
",It
Fig. 1. Polarization Analysis Module
Cameralens for Image Motion Sensor
Polm'izafion Module
Beamsplittex
Fig. 2. Solar Vector Magnetograph Detector Module
An electrically-tunable solid Fabry-Perot etalon /5/ performs the spectral discrimination. Its narrow passband selects for the light from a magnetically sensitive spectral line such as the Fe I line at 630.25 nm. Given the primary's large collecting area, the optical systems' losses, and the desired narrow spectral bandpass, the flux at the surface of the CCD will i~e 108 photons s-larcsec "2. At an image scale of 0.1 " per pixel, each pixel will receive 106 photons s -1. Adopting the performance features of an appropriate CCD, i.e., a quantum efficiency of 50% and a well capacity of 3 x 105 electrons, we get a net accumulation rate of 6 x 105 electrons s -1 pixe1-1. The time required to reach 75% of well capacity is 0.4 s. Since the anticipated read time of the CCD is about 0.8 s, and the total time for each frame will be 1.5 s, the maximum number of frames for each polarization state is 23.3/1.5 = 15. To obtain any Stokes parameter map, including intensity, requires combining two frames, so that the noise level relative to the continuum intensity will be: ~/( 2 S N ) ÷ ( 2 S N ) = 2 x 10"4. In purely statistical terms, this defines the upper limit of the polarization accuracy of the SVMG though whether this can be practically achieved depends upon the entire instrument functioning as designed. The projected experiment capabilities are shown in Table 1. AIR CONVECTION IN THE TELESCOPE The principal reason for carrying out the Flare Genesis Project at 30 km altitude is to escape the image distortions caused by convection in the thermosphere. But, although the SVMG will be above the turbulent layers of the atmosphere, heating of the air near the primary and secondary mirrors could conceivably distort the images. But, Research Support Instruments, Inc./6/found that the air flow across the nearly vertically oriented primary mirror will be stable and laminar, even when the mirror is 20" C hotter than the air (Figure 3). A substantialfurtherincrease in mirror ternperamre could be toleratedbefore turbulence could threaten the image quality,because the air density at 30 k m is only 1.6 % of the density at ground level. TARGET SELECTOR TELESCOPE A compact solar telescope, with a lO-cm aperture, will be aligned with the main telescope. It will form several images of the whole solar disk. One image will be used for coarse-guiding the 80-cm telescope to point anywhere on the Sun to within 10". This image falls on a position-sensitive detector (PSD) that can sense the solar disk center to within 1". Another image falls on a 1024 x 1024 CCD array where it will be only 512 pixels in diameter, but it will have sufficient detail, at 4" per pixel, to reveal interesting targets, such as sunspots. Since we will not be able to communicate with the experiment except for brief periods, the on-board computer must be able to autonomously select the most interesting sunspot groups for targeting the main telescope.
Flare Genesis Project
(2)91
TABLE 1. Experiment capabilities
Spatial resolution: limited by diffraction to 0.2" (140 km at the Sun) Spectral resolution: 0.012 nm passband tunable over spectral line profiles Wavelength range: 600 - 650 nm; Field of view: 100" x 200", with 200" x 200" an option Detector: charge coupled device (CCD), 1024 x 2048 unocculted pixels Exposure interval: 190 s for one magnetogram; 240 s for two interleaved magnetograms Data products: time series of vector magnetograms at various wavelengths, vector velocity and intensity in the photosphere and chromosphere Data storage capacity: 50 Gbytes = 10 tape cassettes each with 1200 images = 200 magnetograms, without data compression, per tape in a 10 cassette loader Telemetry downlink: 768 kbits s-1 (occasional) for target selection 1 kbit s -1 for status checks Detectable solar magnetic field: B z = 1 - 10 G, Bx,y = 50 - 100 G, Velocity sensitivity: ~ 5 m s -1 Intensity sensitivity: ,41/1= 4 x 10-4 single pixel, 10-3 pixel-to-pixel Spectral lines : 1) 630.25 nm, g = 2 . 5 F e I 2) 656.28 nm, g = 1.045 H I (Hot) 3) 638.78 nm; 642.28 nm; 645.81 nm, all clean continua 4) other lines selectable between 580 nm and 680 nm IMAGE ROTATOR The pendulum motion of the gondola causes field rotation, or roll, that must be removed with image rotators, one for the TST and one for the main telescope. The worst-case gondola pendulation is 1800" in 20 s or 90" s- 1 which is much higher than the worst-case diurnal field rotation rate. The image rotator driven by the analog roll gyro signal will easily remove the gondola pendulation field rotation. IMAGE MOTION COMPENSATOR (IMC) The Flare Genesis telescope will be carried in a gondola that will provide 10" pointing stability. By making extensive use of existing gondola designs, e.g.,/7L we believe we can meet this telescope stability requirement. Inside the telescope an image motion compensator will maintain 0.05" image stability. The purpose of the IMC is to keep the image stable during exposure of the CCD, and to keep sequential images registered. The required rms stability of the image is 1/5 pixel or 0.02" over the duration of a magnetogram data sequence (approximately 20 s). Thus, the IMC must provide considerable attenuation of dynamic residual disturbances from the coarse pointing system. The stability requirement on the IMC is very challenging, being only three times looser than the Hubble space telescope pointing requirement. The coarse pointing system residual disturbances can be modeled as the sum of a 0.3" peak-to-peak sinusoid at 5 Hz, due to the balloon momentum transfer system/8/, and a bandlimited white noise floor from 0 to 5 Hz. The rms value of these residual disturbances is on the order of 5". The most difficult disturbance to attenuate is the 5 Hz sinusoid. The 0.3" peak to peak disturbance produces an rms disturbance of0.11". To obtain 0.02" rms performance we will attenuate this disturbance by a factor of 0.11/.02 = 5.5 or 15 dB. ~0 t exp ,_nSt.OOt~ility t~relnotd .
.
.
.
.
.
.
101
10 7
E th instobility threshold 10 S
C' 10 4
tilt 60 deg TO= 2 ternp
¢ 6 difference
8 10 (K}
20
Fig. 3. Grashof number vs. temperature of mirror above ambient (RSI, Inc.)
(2)92
D.M. Rust I N S T R U M E N T CONTROL COMPUTER
The Instrument Control Computer consists of seven VME boards housed in a common chassis. These boards contain the CPU, 64-Mbyte image accumulation memory, SCSI interface controller, 8-channel RS 4 2 2 / 232 controller, analog I/O, Camera interface, telemetry, instrument status, and control (TISC) circuits. The ICC is based on the APL Forth Microprocessor 19/. This CPU is a low-power CMOS microprossesor combined with m e m o r y and peripheral chips on a PC board. Figure 4 is a block diagram of the interfaces between the ICC and the Flare Genesis instrument. At the end of each 140-s magnetograrn sequence, the accumulation memory is reformatted and dumped onto the mass storage device, an Exabyte 8-mm tape drive with a cartridge handling subsystem for 10-tape cartridges. The 2000 calculated observations does not include any image compression. It will be possible to increase the effective storage area by approximately 40% with a lossless image-compression algorithm. These calculations also do not include calibration or instrument housekeeping, which should have only a minor impact. Altil~le [ InmrummtTm Mom~
Guidance Cmurol
ImageMotion Compensator Cca~md & Telemeuy Unit
VottalleLevelamMedulaeon. HighVolUqpMomittr i
RS 422/232 s Chmmel,
i/i~tiii
Telescope 64MByte A~-'umulatieOMemory VSB Bus
"
Cammu~Is
&Smnm
T ~ ~1'cr
~ ~nu'et _ t
Mechanism _...I Commller ~ ~ 8 Charmell
l
Wavepltte ] ---4~t Mechanism [
~m ,~ ~
Blocking Filter
Thermal Controller 8 C~mnels
Tilt Control
SCSI Controller
S~en~and HouseUq~ i::::::i Dam
J
I
Interface
Mats Storage 5 OBytetape, 10 tape loader
tM~
Commm~
Can~ol
~!i~!~
VME
I I SRAM
..sc
L ~__~__
CPU
......
Filter Themml System
Fab~,-Perot Fabry-Perot Tilt HighVoltage Control Amplifier
C,mu~ ]
Commi
I EEI~OM
.-V ~,~o-u-
2 x RS232
Ceetml
~l ! ~ 1 ~
DevelopmentTmminel for GrotmdUse Only lnstrummt Coutrel Computer
CCDCamera CCDCmnem CCDCamera Focus Themutl System Control
Fig. 4. Flare Genesis Instrument Control
Computerinterfaces.
Flare Genesis Project
(2)93
CONCLUSION A detailed study of the anticipated major problem of high-resolution solar imaging on a long-duration balloon flight has been completed. We believe that the difficult tectmical problems of precision pointing and suppression of convection inside the telescope can be overcome. Now, most of the needed components have been procured and are under test. Integration with a gondola is planned for mid-1993, and the first flight is scheduled for January 1994. ACKNOWLEDGEMENTS Among the contributors to the SVMG design study were G. A. Murphy, K. Strohbehn, B. Hochheimer, R. Henshaw, J. R. Hayes, D. A. Lohr, and T. J. Harris, all of APL. J. McKay of Research Support Instruments, Inc., supplied the convection study. This work was supported by the Air Force Office of Scientific Research, Grant AFOSR 90-0102. REFERENCES 1. D. M. Rust, J. W. O'Byme, and T. Harris, An Optical Instrument for Measuring Solar Magnetism, Johns Hopkins APL Tech. Dig. 11, 77 (1988). 2. D. M. Rust, J. W. O'Byrne, and R. E. Sterner, New Instruments for Solar Research, Johns Hopkins APL Tech. Dig. 11, 77 (1990). 3. D. M. Rust and G. Cauzzi, Variation of the Vector Field in an Eruptive Flare, IAU Colloquium 133 "Eruptive Solar Flares', Z. Svestka, B. V. Jackson, and M. E. Machado (eds.), Springer-Verlag Lecture Notes in Physics, 399, p. 46 (1992). 4. M. J. Hagyard, G. A. Gary, and E. A. West, The SAMEX Vector Magnetograph, NASA Technical Memorandum 4048, Marshall Space Flight Center (1988). 5. C.H. Burton, A. J. Leistner, and D. M. Rust, ElectroOptic Fabry-Perot Filter: Development for the Study of Solar Oscillations, Appl. Optics 26, 2637 (1987). 6. Research Support Instruments, Inc., A Balloon-Borne Solar Vector Magnetograph - Phase 1 SBIR Final Report, Research Support Instruments, Inc., CockeysviUe, Maryland (1991). 7. G. Nystrom, P. Cheimets, C. Couvault, J. Grindlay, L. Coyle, F. Licata, and V. Kousmanen, Design of a Lightweight Stabilized Balloon Gondola for X-Ray Observations, Symp. on Thirty Years of Scientific Ballooning in India (1992). 8. Nystrom, G. 1991, private communication. 9. J.R. Hayes, M. E. Fraeman, R. L. Williams, and T. Zaremba, An Instrument Control Processor Using the FORTH Language, in Proc. 2nd Intl. Conf. Architech. Support Prog. Lang. & Oper. Syst., IEEE, p. 42 (1987).
0273-1177/94 $6.00 + 0.00 Copyright © 1993 COSPAR
Printed in Great Britain. All rights reserved.
THE FLARE GENESIS PROJECT D. M. Rust The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, U.S.A.
ABSTRACT The feasibility of a balloon-borne experiment to understand how the magnetic fields at the solar surface emerge, coalesce, unravel and erupt in solar flares was studied. A key component of the Flare Genesis instrument will be a solar telescope with an 0.8-meter-diameter lightweight mirror. Effects of pendulation and jitter, gravity and temperature on the images formed by the telescope were studied to determine whether it will maintain the desired resolution of ~ 0.2 sec of arc at float altitude. The principal conclusions of the study are that (1) sufficient image stability can be maintained at the focal plane; (2) polarization sensitivity of 2 x 10-4 is achievable; and (3) the data system can store ~ 2000 magnetograms on-board in the course of a llYto-14-day Antarctic flight. INTRODUCTION All solar activity arises from the action of magnetic fields. Precise measurements of these fields will be essential for a complete description of the storage, release, and transport of energy in solar flares and other solar activity. The ground-based APL vector magnetograph /1,2/ has confirmed earlier evidence that measurable magnetic field changes probably trigger solar flares/3/. Further observations will doubtless yield added insights, but the potential of ground-based instruments for probing fundamental flare physics is severely limited by turbulence in Earth's atmosphere. We believe that the needed solar observations can be obtained economically in the Antarctic with a balloonborne solar vector magnetograph (SVMG) that can resolve the emerging flux and allow precise correlation of flux changes with flares. The magnetic sensitivity should be sufficient to reveal small changes as fields emerge, submerge or cancel. The SVMG, with 1024 x 2048 0.1"-pixels should lower the 3-o limit for detection of free energy conversion. We estimate the limit at < 1029 ergs over the 1.7'x 3.4' field of view. Many flares with magnetic energy consumption above this level should occur in a two-week balloon flight. INSTRUMENT OVERVIEW Figures 1 and 2 show the focal-plane components of the SVMG. The telescope (not shown) is an F/1.5 Cassegrain with a lightweighted 80-era Zerodur primary mirror and an articulated secondary mirror which produces an F/25 image near the entrance to the polarization module. For thermal control, the primary mirror surface will be overeoated silver or aluminum, which offer at least 95% refiectivity at the operating wavelengths and reduce the thermal loading on the mirror to less than 30 W. The secondary mirror will be transparent except for a narrow spectral band near 630 rim, so most of the 500 watts of collected solar energy will pass through it and exit the telescope. The solar vector magnetic field will be inferred from narrow-band filtergrams obtained at six sequential settings of the polaroids and quarter-waveplate in the Polarization Analysis Module (Figure 2). The filtergrams will correspond to measurements of the Stokes parameters: I + Q, I - Q, 1 + U, I - U, I + v and I - V. /4/. Each six-image sequence, obtained in 8 s, will constitute one vector magnetogram. The random motions of flux tubes on the Sun will limit the time that can be spent accumulating images for each Stokes parameter without loss of resolution. Since a typical flux tube will cross one 0.1" pixel in - 140 s, only seventeen sequences can be averaged together without anyloss in resolution.
JA~q i4:2-6
(2)89
(2)90
D.M. Rust
II 0.12 A Eudon Filter at pupil image ~
I I I I
1.5 A Blocltea"Filta" --._
/ ~
CCD Camera
~
CCD Camera Le~s I~1
Motion
Collimator ~
l
/ --
Field Lens
Hlte~ 200 A passband @ 63oo A
ensor
Microscope Objective
Anermaing7/4P,~eandwindow Rotating polaroid and Z/2 plate
~
Relay Lens
Image Rotator - Pechm Prism
Tilt ~ Mirror
[
image
",It
Fig. 1. Polarization Analysis Module
Cameralens for Image Motion Sensor
Polm'izafion Module
Beamsplittex
Fig. 2. Solar Vector Magnetograph Detector Module
An electrically-tunable solid Fabry-Perot etalon /5/ performs the spectral discrimination. Its narrow passband selects for the light from a magnetically sensitive spectral line such as the Fe I line at 630.25 nm. Given the primary's large collecting area, the optical systems' losses, and the desired narrow spectral bandpass, the flux at the surface of the CCD will i~e 108 photons s-larcsec "2. At an image scale of 0.1 " per pixel, each pixel will receive 106 photons s -1. Adopting the performance features of an appropriate CCD, i.e., a quantum efficiency of 50% and a well capacity of 3 x 105 electrons, we get a net accumulation rate of 6 x 105 electrons s -1 pixe1-1. The time required to reach 75% of well capacity is 0.4 s. Since the anticipated read time of the CCD is about 0.8 s, and the total time for each frame will be 1.5 s, the maximum number of frames for each polarization state is 23.3/1.5 = 15. To obtain any Stokes parameter map, including intensity, requires combining two frames, so that the noise level relative to the continuum intensity will be: ~/( 2 S N ) ÷ ( 2 S N ) = 2 x 10"4. In purely statistical terms, this defines the upper limit of the polarization accuracy of the SVMG though whether this can be practically achieved depends upon the entire instrument functioning as designed. The projected experiment capabilities are shown in Table 1. AIR CONVECTION IN THE TELESCOPE The principal reason for carrying out the Flare Genesis Project at 30 km altitude is to escape the image distortions caused by convection in the thermosphere. But, although the SVMG will be above the turbulent layers of the atmosphere, heating of the air near the primary and secondary mirrors could conceivably distort the images. But, Research Support Instruments, Inc./6/found that the air flow across the nearly vertically oriented primary mirror will be stable and laminar, even when the mirror is 20" C hotter than the air (Figure 3). A substantialfurtherincrease in mirror ternperamre could be toleratedbefore turbulence could threaten the image quality,because the air density at 30 k m is only 1.6 % of the density at ground level. TARGET SELECTOR TELESCOPE A compact solar telescope, with a lO-cm aperture, will be aligned with the main telescope. It will form several images of the whole solar disk. One image will be used for coarse-guiding the 80-cm telescope to point anywhere on the Sun to within 10". This image falls on a position-sensitive detector (PSD) that can sense the solar disk center to within 1". Another image falls on a 1024 x 1024 CCD array where it will be only 512 pixels in diameter, but it will have sufficient detail, at 4" per pixel, to reveal interesting targets, such as sunspots. Since we will not be able to communicate with the experiment except for brief periods, the on-board computer must be able to autonomously select the most interesting sunspot groups for targeting the main telescope.
Flare Genesis Project
(2)91
TABLE 1. Experiment capabilities
Spatial resolution: limited by diffraction to 0.2" (140 km at the Sun) Spectral resolution: 0.012 nm passband tunable over spectral line profiles Wavelength range: 600 - 650 nm; Field of view: 100" x 200", with 200" x 200" an option Detector: charge coupled device (CCD), 1024 x 2048 unocculted pixels Exposure interval: 190 s for one magnetogram; 240 s for two interleaved magnetograms Data products: time series of vector magnetograms at various wavelengths, vector velocity and intensity in the photosphere and chromosphere Data storage capacity: 50 Gbytes = 10 tape cassettes each with 1200 images = 200 magnetograms, without data compression, per tape in a 10 cassette loader Telemetry downlink: 768 kbits s-1 (occasional) for target selection 1 kbit s -1 for status checks Detectable solar magnetic field: B z = 1 - 10 G, Bx,y = 50 - 100 G, Velocity sensitivity: ~ 5 m s -1 Intensity sensitivity: ,41/1= 4 x 10-4 single pixel, 10-3 pixel-to-pixel Spectral lines : 1) 630.25 nm, g = 2 . 5 F e I 2) 656.28 nm, g = 1.045 H I (Hot) 3) 638.78 nm; 642.28 nm; 645.81 nm, all clean continua 4) other lines selectable between 580 nm and 680 nm IMAGE ROTATOR The pendulum motion of the gondola causes field rotation, or roll, that must be removed with image rotators, one for the TST and one for the main telescope. The worst-case gondola pendulation is 1800" in 20 s or 90" s- 1 which is much higher than the worst-case diurnal field rotation rate. The image rotator driven by the analog roll gyro signal will easily remove the gondola pendulation field rotation. IMAGE MOTION COMPENSATOR (IMC) The Flare Genesis telescope will be carried in a gondola that will provide 10" pointing stability. By making extensive use of existing gondola designs, e.g.,/7L we believe we can meet this telescope stability requirement. Inside the telescope an image motion compensator will maintain 0.05" image stability. The purpose of the IMC is to keep the image stable during exposure of the CCD, and to keep sequential images registered. The required rms stability of the image is 1/5 pixel or 0.02" over the duration of a magnetogram data sequence (approximately 20 s). Thus, the IMC must provide considerable attenuation of dynamic residual disturbances from the coarse pointing system. The stability requirement on the IMC is very challenging, being only three times looser than the Hubble space telescope pointing requirement. The coarse pointing system residual disturbances can be modeled as the sum of a 0.3" peak-to-peak sinusoid at 5 Hz, due to the balloon momentum transfer system/8/, and a bandlimited white noise floor from 0 to 5 Hz. The rms value of these residual disturbances is on the order of 5". The most difficult disturbance to attenuate is the 5 Hz sinusoid. The 0.3" peak to peak disturbance produces an rms disturbance of0.11". To obtain 0.02" rms performance we will attenuate this disturbance by a factor of 0.11/.02 = 5.5 or 15 dB. ~0 t exp ,_nSt.OOt~ility t~relnotd .
.
.
.
.
.
.
101
10 7
E th instobility threshold 10 S
C' 10 4
tilt 60 deg TO= 2 ternp
¢ 6 difference
8 10 (K}
20
Fig. 3. Grashof number vs. temperature of mirror above ambient (RSI, Inc.)
(2)92
D.M. Rust I N S T R U M E N T CONTROL COMPUTER
The Instrument Control Computer consists of seven VME boards housed in a common chassis. These boards contain the CPU, 64-Mbyte image accumulation memory, SCSI interface controller, 8-channel RS 4 2 2 / 232 controller, analog I/O, Camera interface, telemetry, instrument status, and control (TISC) circuits. The ICC is based on the APL Forth Microprocessor 19/. This CPU is a low-power CMOS microprossesor combined with m e m o r y and peripheral chips on a PC board. Figure 4 is a block diagram of the interfaces between the ICC and the Flare Genesis instrument. At the end of each 140-s magnetograrn sequence, the accumulation memory is reformatted and dumped onto the mass storage device, an Exabyte 8-mm tape drive with a cartridge handling subsystem for 10-tape cartridges. The 2000 calculated observations does not include any image compression. It will be possible to increase the effective storage area by approximately 40% with a lossless image-compression algorithm. These calculations also do not include calibration or instrument housekeeping, which should have only a minor impact. Altil~le [ InmrummtTm Mom~
Guidance Cmurol
ImageMotion Compensator Cca~md & Telemeuy Unit
VottalleLevelamMedulaeon. HighVolUqpMomittr i
RS 422/232 s Chmmel,
i/i~tiii
Telescope 64MByte A~-'umulatieOMemory VSB Bus
"
Cammu~Is
&Smnm
T ~ ~1'cr
~ ~nu'et _ t
Mechanism _...I Commller ~ ~ 8 Charmell
l
Wavepltte ] ---4~t Mechanism [
~m ,~ ~
Blocking Filter
Thermal Controller 8 C~mnels
Tilt Control
SCSI Controller
S~en~and HouseUq~ i::::::i Dam
J
I
Interface
Mats Storage 5 OBytetape, 10 tape loader
tM~
Commm~
Can~ol
~!i~!~
VME
I I SRAM
..sc
L ~__~__
CPU
......
Filter Themml System
Fab~,-Perot Fabry-Perot Tilt HighVoltage Control Amplifier
C,mu~ ]
Commi
I EEI~OM
.-V ~,~o-u-
2 x RS232
Ceetml
~l ! ~ 1 ~
DevelopmentTmminel for GrotmdUse Only lnstrummt Coutrel Computer
CCDCamera CCDCmnem CCDCamera Focus Themutl System Control
Fig. 4. Flare Genesis Instrument Control
Computerinterfaces.
Flare Genesis Project
(2)93
CONCLUSION A detailed study of the anticipated major problem of high-resolution solar imaging on a long-duration balloon flight has been completed. We believe that the difficult tectmical problems of precision pointing and suppression of convection inside the telescope can be overcome. Now, most of the needed components have been procured and are under test. Integration with a gondola is planned for mid-1993, and the first flight is scheduled for January 1994. ACKNOWLEDGEMENTS Among the contributors to the SVMG design study were G. A. Murphy, K. Strohbehn, B. Hochheimer, R. Henshaw, J. R. Hayes, D. A. Lohr, and T. J. Harris, all of APL. J. McKay of Research Support Instruments, Inc., supplied the convection study. This work was supported by the Air Force Office of Scientific Research, Grant AFOSR 90-0102. REFERENCES 1. D. M. Rust, J. W. O'Byme, and T. Harris, An Optical Instrument for Measuring Solar Magnetism, Johns Hopkins APL Tech. Dig. 11, 77 (1988). 2. D. M. Rust, J. W. O'Byrne, and R. E. Sterner, New Instruments for Solar Research, Johns Hopkins APL Tech. Dig. 11, 77 (1990). 3. D. M. Rust and G. Cauzzi, Variation of the Vector Field in an Eruptive Flare, IAU Colloquium 133 "Eruptive Solar Flares', Z. Svestka, B. V. Jackson, and M. E. Machado (eds.), Springer-Verlag Lecture Notes in Physics, 399, p. 46 (1992). 4. M. J. Hagyard, G. A. Gary, and E. A. West, The SAMEX Vector Magnetograph, NASA Technical Memorandum 4048, Marshall Space Flight Center (1988). 5. C.H. Burton, A. J. Leistner, and D. M. Rust, ElectroOptic Fabry-Perot Filter: Development for the Study of Solar Oscillations, Appl. Optics 26, 2637 (1987). 6. Research Support Instruments, Inc., A Balloon-Borne Solar Vector Magnetograph - Phase 1 SBIR Final Report, Research Support Instruments, Inc., CockeysviUe, Maryland (1991). 7. G. Nystrom, P. Cheimets, C. Couvault, J. Grindlay, L. Coyle, F. Licata, and V. Kousmanen, Design of a Lightweight Stabilized Balloon Gondola for X-Ray Observations, Symp. on Thirty Years of Scientific Ballooning in India (1992). 8. Nystrom, G. 1991, private communication. 9. J.R. Hayes, M. E. Fraeman, R. L. Williams, and T. Zaremba, An Instrument Control Processor Using the FORTH Language, in Proc. 2nd Intl. Conf. Architech. Support Prog. Lang. & Oper. Syst., IEEE, p. 42 (1987).