The Ultra Fast Flash Observatory pathfinder (UFFO-p) is a telescope system designed for the detection of the prompt optical/UV photons from Gamma-Ray Bursts (GRBs), and it will be launched onboard the Lomonosov spacecraft in 2012. The UFFO-p consists of two instruments: the UFFO Burst Alert and Trigger telescope (UBAT) for the detection and location of GRBs, and the Slewing Mirror Telescope (SMT) for measurement of the UV/optical afterglow. The UBAT isa coded-mask aperture X-ray camera with a wide field of view (FOV) of 1.8 sr. The detector module consists of the YSO(Yttrium Oxyorthosilicate) scintillator crystal array, a grid of 36 multi-anode photomultipliers (MAPMTs), and analog and digital readout electronics. When the γ /X-ray photons hit the YSO scintillator crystal array, it produces UV photons by scintillation in proportion to the energy of the incident γ /X-ray photons. The UBAT detects X-ray source of GRB inthe 5 ~ 100 keV energy range, localizes the GRB within 10 arcmin, and sends the SMT this information as well as drift correction in real time. All the process is controlled by a Field Programmable Gates Arrays (FPGA) to reduce the processing time. We are in the final stages of the development and expect to deliver the instrument for the integration with the spacecraft. In what follows we present the design, fabrication and performance test of the UBAT.
We describe the space project of Ultra-Fast Flash Observatory (UFFO) which will observe early optical photons from
gamma-ray bursts (GRBs) with a sub-second optical response, for the first time. The UFFO will probe the early optical
rise of GRBs, opening a completely new frontier in GRB and transient studies, using a fast response Slewing Mirror
Telescope (SMT) that redirects optical path to telescope instead of slewing of telescopes or spacecraft. In our small
UFFO-Pathfinder experiment, scheduled to launch aboard the Lomonosov satellite in 2012, we use a motorized mirror in
our Slewing Mirror Telescope instrument to achieve less than one second optical response after X-ray trigger. We
describe the science and the mission of the UFFO project, including a next version called UFFO-100. With our program
of ultra-fast optical response GRB observatories, we aim to gain a deeper understanding of GRB mechanisms, and
potentially open up the z<10 universe to study via GRB as point source emission probes.
Since the launch of the SWIFT, Gamma-Ray Bursts (GRBs) science has been much progressed. Especially supporting
many measurements of GRB events and sharing them with other telescopes by the Gamma-ray Coordinate Network
(GCN) have resulted the richness of GRB events, however, only a few of GRB events have been measured within a
minute after the gamma ray signal. This lack of sub-minute data limits the study for the characteristics of the UV-optical
light curve of the short-hard type GRB and the fast-rising GRB. Therefore, we have developed the telescope named the
Ultra-Fast Flash Observatory (UFFO) Pathfinder, to take the sub-minute data for the early photons from GRB. The
UFFO Pathfinder has a coded-mask X-ray camera to search the GRB location by the UBAT trigger algorithm. To
determine the direction of GRB as soon as possible it requires the fast processing. We have ultimately implemented all
algorithms in field programmable gate arrays (FPGA) without microprocessor. Although FPGA, when compared with
microprocessor, is generally estimated to support the fast processing rather than the complex processing, we have
developed the implementation to overcome the disadvantage and to maximize the advantage. That is to measure the
location as accurate as possible and to determine the location within the sub-second timescale. In the particular case for a
accuracy of the X-ray trigger, it requires special information from the satellite based on the UFFO central control system.
We present the implementation of the UBAT trigger algorithm as well as the readout system of the UFFO Pathfinder.
The Slewing Mirror Telescope (SMT) is a key telescope of Ultra-Fast Flash Observatory (UFFO) space project to
explore the first sub-minute or sub-seconds early photons from the Gamma Ray Bursts (GRBs) afterglows. As the
realization of UFFO, 20kg of UFFO-Pathfinder (UFFO-P) is going to be on board the Russian Lomonosov satellite in November 2012 by Soyuz-2 rocket. Once the UFFO Burst Alert & Trigger Telescope (UBAT) detects the GRBs,
Slewing mirror (SM) will slew to bring new GRB into the SMT’s field of view rather than slewing the entire spacecraft. SMT can give a UV/Optical counterpart position rather moderated 4arcsec accuracy. However it will provide a important understanding of the GRB mechanism by measuring the sub-minute optical photons from GRBs. SMT can respond to the trigger over 35 degree x 35 degree wide field of view within 1 sec by using Slewing Mirror Stage (SMS). SMT is the reflecting telescope with 10cm Ritchey-Chretien type and 256 x 256 pixilated Intensified Charge-Coupled Device (ICCD). In this paper, we discuss the overall design of UFFO-P SMT instrument and payloads development status.
The UFFO (Ultra-Fast Flash Observatory) Pathfinder is a space instrument onboard the Lomonosov satellite scheduled
to be launched in November 2011. It is designed for extremely fast observation of optical counterparts of Gamma Ray
Bursts (GRBs). It consists of two subsystems; i) UBAT (UFFO Burst Alert & Trigger Telescope) and ii) SMT (Slewing
Mirror Telescope). This study is concerned with SMT opto-mechanical subsystem design and optical performance test.
SMT is a F/11.4 Ritchey-Chretien type telescope benefited from compact design with a short optical tube assembly for
the given focal length of 1,140 mm. SMT is designed to operate over a wide range of wavelength between 200 nm and
650 nm and has 17 arcmin FOV (Field of View), providing 4 arcsec in detector pixel resolution. The main detector is
256 x 256 ICCD (Intensified Charge-Coupled Device) of 22.2μm in pixel size. This SMT design offers good imaging
performance including 0.77 in MTF at Nyquist frequency of 22.52 /mm and 2.7 μm in RMS spot radius. The primary
(M1) and secondary (M2) mirror are hyperbolic surfaces and were manufactured within 1/50 waves (He-Ne, 632.8nm) in
RMS surface error. After completion of the initial integration, the SMT opto-mechanical subsystem reached to the
system wavefront error better than 1/10 waves in room temperature. We then tested the opto-mechanical performances
under thermal cycling and vibration. In this study, we report the SMT subsystem design solution and integration together
with thermal and vibration test results.