Imaging attitude finder for a sounding rocket and magnesium ion... airglow spatial pattern N. Iwagami , Y. Koizumi-Kurihara

An Introduction to Space Instrumentation,
Edited by K. Oyama and C. Z. Cheng, 21–24.
Imaging attitude finder for a sounding rocket and magnesium ion imager for
airglow spatial pattern
N. Iwagami1 , Y. Koizumi-Kurihara2 , and J. Kurihara3
1 Department
2 Institute
of Earth and Planetary Science, University of Tokyo, Japan
of Space and Astronautical Science, Japan Aerospace Exploration Agency, Japan
3 Graduate School of Science, Hokkaido University, Japan
The IAF (Imaging Attitude Finder) is an imager using a one-dimensional multi-anode photomultiplier, and
determines the attitude of a spinning sounding rocket with a precision of +/− 0.6◦ by finding out stars. One of
the applications of IAF, MII (Magnesium Ion Imager) is a UV version of the former optimized for measuring the
Mg+ twilight airglow occurring at around 100 km, and images its horizontal structures by looking it from above.
Key words: Rocket attitude, star finding, magnesium ion, twilight airglow.
1.
Introduction
2.
It is usually needed to know the attitude of a sounding
rocket for scientific and/or technical purpose. For example, in-situ measurement of electric field needs information about the attitude because the induced electric field
E = Vrocket × Bearth depends sensitively on the difference
between the rocket-velocity vector and the spin-axis vector
(e.g. Nakamura et al., 1998). The NTV (N2 Temperature
of Vibration) measurement also needs attitude information
because the shock wave produced by the super-sonic speed
of the rocket may disturb the environment to be measured
(Kurihara et al., 2006). Optical remote measurements such
as of airglow also need information about the direction of
the line of sight because the effect due to the slant ray path
may play an important role in quantification (e.g. Iwagami
et al., 2003). In daytime, a combination of a magnetometer
and a sun-sensor works well to find out the absolute attitude;
however, the latter may not be used in nighttime. It must be
noted that at least a couple of independent information is
usually needed to determine the absolute attitude.
In nighttime a sort of STS (Star Sensor) with single eye
had been used for the sounding rocket experiment up to
1992 (see Table A1). It could determine the absolute attitude by itself; however, the small field of view (2.5◦ square)
did not allow providing good data set because of limited
number of identified stars. It was improved later to have
an N-shaped slit (10◦ square: Iwagami et al., 1998, in
Japanese), and succeeded to see four times more stars with
better directional resolution. In the present paper, an improved version of STS with 8 eyes named the IAF (Imaging
Attitude Finder) is described. It can also determine the absolute direction of the spin-axis of a rocket without any help
from another attitude sensor. This is an important advantage
of such kind of sensor; however, its disadvantage is in the
complexity in the analysis procedure as will be noted in a
latter section.
Instrumentation
In Fig. 1 the outlook (top) and the cross section (bottom)
of the IAF are represented. It consists of an achromatic lens,
a mask with a 4 mm × 8 mm aperture, a PMT (photomultiplier tube), a HV (high voltage) supply and electronics. The
lens has a focal length of 50 mm and an aperture of 28 mm.
The mask placed on the focal plane selects 8 anodes of the
PMT in its 8 mm width. Although the PMT R5900U-00L16 manufactured by Hamamatsu Photonics has 16 anodes,
only 8 of them are used mostly due to limited data processing rate of the telemetry system. The pitch of the anodes
is 1 mm corresponding to an angle of 1.15◦ , and the total
angular width of 8 anodes is 9.2◦ . The PMT is small just
having a size of 30 mm square × 41 mm in length including a connector as seen in Fig. 1. The PMT has a bi-alkali
photo-cathode having sensitivity in the 300–650 nm region.
Both PMT and the HV supply are set in an airtight box to
prevent them from discharging. Each anode has high (×10)
and low (×1) gain output channels. The minimum bit rate
needed is 25.6 kbps (8 bit × L and H × 200 Hz sampling
× 8 anodes) .The main part of the electronics is separated,
and not shown in the figure.
Since the line of sight of the IAF is usually set at 30◦
away from the spin-axis, and the spinning period is about
one sec (in case of the S-310 type rocket), the instantaneous
field of view (4.6◦ × 9.2◦ ) sweeps the star field in a doughnut shaped region with an inner and outer radiuses of 25◦
and 35◦ , respectively, in a period of one second as illustrated in Fig. 2. From the pattern of signals due to stars,
the direction of the spin-axis is determined if two or more
stars are identified during one spin cycle. The 4 mm (4.6◦ )
length of the mask determines the duration of one star pulse
(24 ms in the nominal case). The analysis procedure must
take this duration into account.
3.
Adjustments and Calibration
The focus is adjusted by checking an image of a point
light source in a laboratory with visible inspection, and the
sensitivity is adjusted by using a star or a planet such as
Jupiter. Usually the full scale of the high gain channel is
c TERRAPUB, 2013.
Copyright 21
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N. IWAGAMI et al.: IMAGING ATTITUDE FINDER AND MAGNESIUM ION IMAGER
..
..
Fig. 1. Outlook (top) and cross section (bottom) of the IAF.
..
Fig. 2. Schematic illustration of the field of view of the IAF synthesized
by the spinning motion. The instantaneous field of view (4.6◦ × 9.2◦ by
8 anodes) sweeps the star field to form a doughnut-shaped region with
inner and outer radiuses of 25◦ and 35◦ , respectively.
set to the output of a star of the first magnitude. The main
part of the data is expected to be obtained in the high-gain
channel; however, the low-gain channel is sometimes useful
because of unexpected disturbances such as due to aurora,
moonlight, and twilight.
These procedures cannot simply be applied to the MII
because its wavelength 280 nm is not visible as will be
described in a latter section.
4.
Examples of Results
In Fig. 3, examples of the measured directions of the
spin axis of the sounding rocket S-310-33 (Iwagami et al.,
2005a, b, in Japanese) are plotted. After the launch, the
zenith angle of the spin axis increases gradually as far as
air drug works. At around 90 km in ascent, air drug dis-
Fig. 3. Examples of observed directions of the spin-axis. The numbers
shown in the figure are spin numbers starting at the beginning of the
measurement at around 60 km in ascent. Every direction is shown for
the 1st–10th and the 220th–227th spin numbers, and every 5 direction
is shown for the 10th–220th; however, there are some deficiency in data
such as between 105th and 120th. The zenith, the launching direction
and the direction of the geomagnetic line of force are indicated by Z, L
and M, respectively (figure after Iwagami et al., 2005b).
..
Fig. 4. Schematic illustration of the two-dimensional observation of the
Mg+ airglow occurring at around 100 km seen from the MII flying
above it. Although the instantaneous field of view is 1.25◦ × 10.0◦ by
8 anodes, it sweeps a doughnut-shaped aria at 100 km by utilizing the
spinning motion of the rocket with a period of about one second (figure
after Kurihara et al., 2010).
appears, and the precession motion begins. Usually the radius of the precession motion is 10◦ –20◦ with a period of
150 s–250 s (see Table A1). It continues until the attitude
of the rocket start to change due to drug by thick atmosphere at around 90 km in descent. In case of the S-31033 experiment shown in the figure, the steady precession
motion started at around the spin number 20 (80.84 s after
the launch at 89.5 km) and ended at around the spin number 222 (291.92 s after the launch at 89.7 km). However,
it must be noted that the successful determination depends
mostly on fortunate capture of stars happen to come into
the field of view. At some unfortunate occasions such as
seen in between the spin numbers 105 and 120, no solution
N. IWAGAMI et al.: IMAGING ATTITUDE FINDER AND MAGNESIUM ION IMAGER
23
the full scale of the high gain channel was set to 11.2 kR
although the expected radiance of the Mg+ airglow was
1 kR (Kurihara et al., 2010) because a serious superposition
of the Rayleigh scattered sunlight was anticipated.
In Fig. 5, the horizontal structure of the Mg+ twilight
airglow seen from the MII flying above the airglow layer
(Kurihara et al., 2010) is shown. The 30 km (0.3◦ in latitude) scale structures seen in the horizontal distribution
seems to be due to modulation by the atmospheric gravity waves coming from the lower atmosphere, and seem to
support the wind shear scenario to cause the Es event.
..
Fig. 5. Horizontal distribution of the Mg+ airglow found by the MII.
The wavy structures with a scale of 30 km (0.3◦ in latitude) suggest a
modulation due to atmospheric gravity waves (figure after Kurihara et
al., 2010).
6.
Remaining Problems and Future Improvements
The largest disadvantage of the IAF is its complexity
in the data analysis. The identification of stars has not
been automated, and still needs human handling. It will be
improved if suitable software is introduced for identifying
was obtained; this is because at least two stars (hopefully stars. Or it may already be possible to use a couple of GPS
three stars) must be identified during one spin cycle to fix (global positioning system) sensors placed at the top and the
one spin-axis direction. The rms (root mean square) ran- bottom of a rocket to find out the spin-axis direction.
dom error is estimated by fitting a precession circle to the
data points to be 0.6◦ in the present case; however, it must Acknowledgments. The authors thank to Mr. H. Tamura and his
be noted that this is the most fortunate example, and some- colleagues of EiDii Co. for manufacturing the IAF and the MII,
and also to all the people involved in the sounding rocket experitimes only a fragment of a precession circle is obtained.
ments.
5.
Application of IAF (MII)
The MII (Magnesium Ion Imager) is a UV version of the
IAF just added an UV interference filter for measuring the
Mg+ 279.6 and 280.3 nm doublet twilight airglow. This
airglow is related closely to the Es (sporadic E layer) event,
and is expected to show its formation process. If such
process is connected to modulation by atmospheric waves
or instabilities, some horizontal wavy patterns should be
seen in the airglow structure. The aim of the MII is to look
for such structure on board a sounding rocket flying above
them (Kurihara et al., 2010).
Some modifications from IAF are there in its instrumentation. In case of the S-310-38 rocket experiment (Kurihara
et al., 2010), an interference filter with a center wavelength
of 278.4 nm and a FWHM (full width of a half maximum)
of 16.3 nm was added in front of the lens. A fused silica single lens was used in place of an achromatic lens because the latter does not work in the UV region. The PMT
used is R5900U-06-L16 having a sensitive wavelength region of 160–650 nm with a silica window and a mask of
1 mm × 8 mm. Because of the smaller mask and the shorter
wavelength than for the IAF, the instantaneous field of view
(1.25◦ × 10.0◦ ) is much shorter but a little wider than that
for the IAF (4.6◦ × 9.2◦ ). The line of sight of the MII was
set downward 30◦ away from the spin-axis of the rocket to
see the horizontal pattern appearing in the Mg+ airglow distribution occurring at around 100 km from the rocket flying
above it as illustrated in Fig. 4.
The focus adjustment needs the following two steps: (1)
adjustment by using a lamp with inspection of its visible
image and (2) correction of the focus position by using
calculated difference in the focal lengths between visible
and UV. The sensitivity is adjusted by using a UV lamp with
a known irradiance. In case of the S-310-38 experiment,
Appendix A
The attitudes of the S-310 type sounding rocket measured by
the IAF and its ancestor STS (star sensor) so far are summarized
in Table A1. The measured parameters of the circular precession
motion (direction of the center, radius, period and duration) as well
as the launching parameters are listed. They should be important
information for future scientific planning as well as for technical
purpose such as in designing the new rocket of the next generation.
References
Iwagami, N., Attitude determination of a sounding rocket with a star sensor, ISAS (Institute of Space and Astronautical Science) report special
issue 38, 69–74, 1998. (in Japanese)
Iwagami, N., T. Shibaki, T. Suzuki, H. Sekiguchi, N. Takegawa, and W.H.
Morrow, Rocket observation of atomic oxygen density and airglow
emission rate in the WAVE2000 campaign, J. Atmos. Solar-Terr. Phys.,
65, 1349–1360, 2003.
Iwagami, N., S. Ohtsuki, M. Akojima, M. Kubota, Y. Murayama, S. Kawamura, R. Yoshimura, T. Nakamura, H. Yamamoto, H. Sekiguchi, N.
Kimura, K. Shiokawa, T. Okada, K. Ishisaka, Y. Ashihara, Y. Kaiho,
M. Abo, T. Abe, Y. Koizumi, and K-I. Oyama, Waves in airglow experiment 2004: Overview and preliminary results, Adv. Space Res., 35(11),
1964–1970, 2005a.
Iwagami, N., M. Akojima, and S. Ohtsuki, Atomic oxygen density, airglow
emission rate and attitude of the rocket for the Wave 2004 campaign,
JAXA (Japan Aerospace Exploration Agency) Report SP-04-007, 2005b.
(in Japanese)
Kurihara, J., K.-I. Oyama, N. Iwagami, and T. Takahashi, Numerical simulation of 3D flow around sounding rocket in the lower thermosphere,
Ann. Geophys., 24, 89–95, 2006.
Kurihara, J., Y. Koizumi-Kurihara, N. Iwagami, T. Suzuki, A. Kumamoto,
T. Ono, M. Nakamura, M. Ishii, A. Matsuoka, K. Ishisaka, T. Abe, and
S. Nozawa, Horizontal structure of sporadic E layer observed with a
rocket-borne magnesium ion imager, J. Geophys. Res., 115, A12318,
2010.
Nakamura, M., H. Noda, I. Yoshikawa, N. Iwagami, M. Hirahara, M.
Yamamoto, and S. Fukao, DC electric field measurement in the SEEK
campaign, Geophys. Res. Lett., 29, 1777–1780, 1998.
N. Iwagami (e-mail: [email protected]), Y. Koizumi-Kurihara,
and J. Kurihara
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N. IWAGAMI et al.: IMAGING ATTITUDE FINDER AND MAGNESIUM ION IMAGER
Table A1. Measured attitude parameters of the past S-310 type rockets with launching conditions.
Rocket ID
Sensor type
S-310-38
8-eye IAF
Launch date
Launch direction
lza∗1b laa∗2b
06Feb2008
18◦ 135◦
Precession circle
cza∗1 caa∗2 radius
period cycles∗3
30◦ 85◦ 25◦
300 s 0.8
S-310-33
8-eye IAF
18Jan2004
18◦ 135◦
32◦ 125◦ 18◦
226 s 0.9
wave2004 campaign
bad attitude due to low launch angle?
S-310-32
8-eye IAF
03Aug2003
20◦ 107◦
43◦ 65◦ 27◦
220 s 0.7
seek2 campaign
bad attitude due to low launch angle?
S-310-31
8-eye IAF
03Aug2003
18◦ 107◦
38◦ 92◦ 7◦
238 s 1.1
seek2 campaign
S-310-30
4-eye IAF
06Feb2002
12◦ 135◦
28◦ 160◦ 12◦
150 s 0.8
2nd NTV∗4 experiment
motor separation at 199 s
S-310-29
N-slit STS∗6
10Jan2000
13◦ 135◦
17◦ 117◦ 8◦
192 s 1.5
wave2000 campaign
S-310-26
N-slit STS
21Aug1996
15◦ 100◦
15◦ 165◦ 16◦
230 s 1.2
seek1 campaign
TMA∗5 ejection at 284 s
S-310-25
N-slit STS
26Aug1996
15◦ 100◦
18◦ 135◦ 10◦
190 s 1.6
seek1 campaign
S-310-24
N-slit STS
11Feb1996
14◦ 135◦
25◦ 120◦ 28◦
180 s 1.9
1st NTV experiment
bad attitude due to low launch angle?
S-310-21
1-eye STS
28Jan1992
8◦ 135◦
17◦ 154◦ 12◦
192 s 1.9
3rd O experiment
S-310-20
1-eye STS
28Jan1990
12◦ 148◦
28◦ 138◦ 8◦
210 s 1.5
2nd O experiment
S-310-19
01Feb1989
7◦ 89◦ 9◦
1-eye STS
12◦ 144◦
210 s 1.9
∗1 cza (center zenith angle)
∗1b lza (launch zenith angle)
∗2 caa (center azimuth angle: from north eastward)
∗2b laa (launch azimuth angle)
∗3 cycles (number of precession circles completed)
∗4 NTV (nitrogen temperature of vibration)
∗5 TMA (trimethyl aluminum: glowing matter)
∗6 STS (star sensor)
Notes
disturbed data due to twilight
bad attitude due to low launch angle?
1st O experiment