Hyper Gravity-Induced Transients in Phycomyces as Measured by Single Beam Spectrophotometer on the Sounding Rocket TEXUS 50

In the first paper of two referring to the TEXUS 50 campaign using micro dual wavelength spectrometers (MDWS) we kinetically determined the threshold for GIACs (gravity-induced absorption changes) in Phycomyces to be lower than 25 × 10 g (http://file.scirp.org/pdf/JMP_2015082810060783.pdf). In this second paper, we attended measurement of GIAC-spectra. Unexpectedly, during the upwards movement, i.e. the hypergravity phase up to top acceleration values reaching 11.6 g at 35.4 s after liftoff we observed transient GIAC-spectra ranging from 380 to 750 nm. In addition, during the whole acceleration phase of 68.2 s, another component near 700 nm develops which remains stable during the whole “free fall trajectory parabola” for 381.3 s. The subsequent reentry of the rocket leads to extraordinary deceleration values up 37.8 g, completely destroying Phycomyces sporangiophores excluding their spectral measurement. During the microgravity phase and by centrifuge operation we were unable to detect any GIAC-spectra (in contrast to kinetic MDWS-measurements, first paper).


Introduction
The Micro Dual Wavelength Spectrometer (MDWS) only allows measurements at individual wavelengths of the spectrum defined by selected light emitting diodes (LEDs) [1]. It does not allow to measure complete spectra with a comparable high sensitivity. Therefore, we attempted a complementary measurement of the complete spectrum of GIACs in Phycomyces sporangiophores (SPPHs, Figure 1), during the start phase of hypergravity and the subsequent phase of microgravity using a single beam spectrophotometer (diode array spectrophotometer SBS, USB-2000+ by Ocean Optics). However, due to its fundamentally much lower sensitivity of the SBS compared to the MDWS we were not able to detect any GIACs on a spectral basis during the microgravity phase. During our first evaluation of the TEXUS 50 data [1] we only focussed on the originally envisaged data obtained during microgravity, ignoring data obtained during the start phase, i.e. hypergravity. Surprisingly, just during the phase of strong hypergravity (0 to 37 s, acceleration up to 11.6 g) we observed pronounced and intermediate GIAC-spectra. In addition, another but smaller peak comes up during the late state of hypergravity, further standing in the subsequent microgravity phase.
These GIACs generated under hypergravity conditions appear to be of biological rather than artificial background.

Sounding Rocket TEXUS 50
We participated in the 50 th jubilee sounding rocket campaign: (http://www.spacedaily.com/reports/Swedish_Space_Corporation_Celebrates_50 th_Anniversary_of_Esrange_Space_Center_999.html). The Texus 50 was started on the 12 th of April 2013, burn out of the first rocket motor after 11.6 s at a height of about 8 km, burn out of the second rocket motor after 43.9 s at a height of about 100 km reaching a velocity of app. 10100 km h −1 . After "YoYo-despin"

The Two Applied Concepts of Optical Spectroscopy
The Micro Dual Wavelength Spectrometer (MDWS) has been developed by us and described previously in more detail [2] [3]. The MDWS is capable of measuring extremely small optical absorption/reflection changes (<10 −5 A) and is at least 1000 times more sensitive(!) than common double and single beam spectrophotometers, depending on the measuring conditions [4]. More details are given in the first paper [1]. reflectance rather than absorption as suggested by its name. Important to note generally: when measuring very small optical signals in various SBS-modes such as absorption, fluorescence or reflection the absolute measure is inevitably lost (e.g. dark currents, light scattering, see [4]). Thus, the baseline has to be defined manually (cf. Figure 4, Figure 5, Figure 7, Figure 10). Nevertheless, due to the relative small amount of reflected light reaching the entrance of the spectrometer only a poor SNR 3 is attained, anyway. However, after extensive averaging and by FFT 2 -smoothing using a suitable kernel for the integral, valuable information can be extracted even from noisy signals. Figure 3 shows the 3D-plot of all four spectrophotometers embedded in the TEXUS 50 rocket (flight implementation plan by Astrium, MDWS, SBS; module TEM 06-33). A fixed platform is located in the upper part of the module, the rotary platform in the middle part. A 3D-magnetometer (not seen in this plot) is localized just below the fixed and on top the rotary platform (playing the essential role in the 3 rd forthcoming paper of this series). The bottom part contains the electronics, batteries and the motor drive of the rotary platform.

Strains and Culture Conditions
The left side of Figure 1 shows a hedge of SPPHs of Phycomyces blakesleeanus (Burgeff), NRRL1555 (-) originally obtained from the Northern Regional Research Laboratory, USDA, Peoria, IL, USA. Sporangiophores of Phycomyces were raised as described previously [5].

Telemetry
The on board experiment is completely controlled and monitored from the base station via radio signals (TCE64-Telecommand-Encoder for 64 digital signals).
These include various parameters such as currents of LEDs, averaging, boxcar,

Results and Discussion
We measured 1281 (uncorrected) individual reflection spectra ranging from 350 to 850 nm during the start-(hypergravity, 0 to 68.2 s) and the subsequent microgravity phase (<10 −5 g between 68.2 s to 449.5 s) as shown in Figure 4. Thus, 3.36 spectra per second were monitored. The observed changes are large and the spectra are from the beginning of microgravity "compressed" to a single spectrum. In addition, 15 s after the liftoff another group of "densified" spectra is observed. This is explained by the (uncorrected) kinetical GIAC-signals for various wavelengths indicated as obtained by the SBS. Figure 5 Figure   5(b) represents the main g-value in flight direction (G z ).
Just after liftoff the G z signal decreases for 3 s from 7 to 3.8 g (rocket is set to rotation) to increase again to 6 g, when the first rocket motor is separated after  11.6 g, > 2 g by rockets rotation) are large and the spectra are from the beginning of microgravity "compressed" to a single spectrum. In addition, 15 s after liftoff there comes up another group of compressed spectra, which is explained below.
12 s at a height about 8 km. Then, for 3 s G z is −1 g (ground situation) and subsequently the rocket is boosted by the second motor up to a height approx. 100 km experiencing a maximum of 11.6 g after 35.5 s and a velocity of 10,100 km/h.
Concluding, the course of the hypergravity-induced GIAC ( Figure 5(a)) does not at all reflect the directly measured gravity course ( Figure 5(b)). This is taken to indicate a biological intermediate rather than a (trivial) artifact which is further supported by the corrected GIAC-spectra and the MDWS signal as follows.    [1], the SBS does not allow detecting the expected miniscule GIAC signals on a spectral basis. This reminds us of the fact that the well-studied plant photoreceptor Phytochrome also has never been measured in vivo other than by dual wavelength spectroscopy. Only after considerable accumulation the first spectral measurement of Phytochrome could be performed in vitro [6]. The (uncorrected)    A series of earth-bound test spectra of dummies made from thin copper wire (diameter 50 µm,) representing the Phycomyces sporangiophore ( Figure 1) is shown in Figure 10 to 25 arbitrary units. Figure 10(b) Clearly, the calculated reflection/absorption changes essentially show straight lines and do not cause distinctive "spectra", suggesting that the observed GIACs in Figure 6 are real and not trivial "mechanical artefacts", as could be claimed.

Conclusion
This present paper shows for the first time that hypergravity induces both Figure 9. (a) shows the section of Figure 4 between 650 and 800 nm. Clearly, with the decreasing GIAC-signal at decreasing hypergravity another broad peak at 700 nm evolves. (b) long term GIACs (after 15, 30, 60 min) and LIAC (45') in SPPHs as measured some 18 years ago [8]. Clearly, under standard conditions (1 g) if SPPHs are tilted in the horizontal position GIACs slowly develop with characteristic broad spectral peaks at 700, 540 and 420 nm.
However, only the peak at 700 nm clearly appears to develop under (fast) hypergravity. Synopsis of both papers referring to Texus 50, [1] and the present one clearly demonstrate the superior sensitivity of dual wavelength compared to single beam spectroscopy: GIACs observed under microgravity conditions by dual wavelength spectroscopy cannot be seen by common single beam spectroscopy.