Proc. of the GHOU 2007 in Tokyo

Using JAXA's Space Science Data for Education and Public Outreach

KenEbisawa*1

JAXA (Japan Aerospace Exploration Agency) is Japan's sole space organization, which is launching space science missions such as astronomical satellites, lunar and planetary missions and solar-terrestrial physics satellites, as well as practical missions such as whether satellites and communication satellites. I will introduce JAXA's space satellite missions and data, and our efforts to utilize these data for education and public outreach purposes.

1. Introduction

Currently, JAXA's three astronomical satellites, Suzaku (X-rays), Akari (infrared) and Hinode (Solar), are operational, and continuously taking superior data in each field of astronomy. Furthermore,Hayabusa, an asteroid sample return mission, has produced excellent images of the asteroid Itokawa. The SELENE lunar orbiter, named “Kaguya” after the launch on Sep 14, 2007, is going to provide the most complete lunar reconnaissance data as well. Most of these data taken by JAXA satellites will become public after short proprietary periods, and be freely used not only for scientific researches but also for educational purposes and public outreach.

We are maintaining the JAXA’s space science archives named DARTS (Data ARchives and Transmission System; which keeps most extensive Japanese scientific satellite database (Fig.1). DARTS’s prime purpose is to serve professional space scientists all over the world, butit may be used by educators and/or students.

Since DARTS is designed for professional scientist, significant efforts are required to make these data reachable to teachers and students, and to maximally utilize these precious data for education. We have a plan to start such systematic efforts in collaboration withJAXA’s scientists and educators.

2. Using X-ray Data in Education

As an example, I will present some ideas to utilize X-ray satellite data for education, since I myself am an X-ray astronomer. X-ray satellite date, from educational point of view, have the following characteristics: (1) Almost all the X-ray astronomical satellite data are archived. Usually, after one-year proprietary period, data are put in the archives, and everybody may freely use them. (2) Data are highly processed. Users do not need to calibrate or reduce the data, but they can immediately start data “analysis” (Fig.2). (3) X-ray astronomy is a scientific field Japan is particularly strong at. Japan has been launching five X-ray satellites, and there are more than 100 professional Japanese X-ray astronomers, who are diversely distributed at universities or institutes all over Japan.

I present two examples of the lesson plans using X-ray data in the following.

Timing analysis of Crab pulsar:

Since X-ray photon can be counted by detectors one-by-one, we will have “an X-ray event file” when photon events are recorded. For each X-ray event, the photon arrival time is recorded with an accuracy of up to microseconds. For fast-rotating pulsars, such as Crab pulsar (P~30msec), the pulsation can be readily seen from the list of photon arrival time.

If you see the raw light curve by naked eye, you may not notice the pulsation, since signal-to-noise ratio is too small. However, if you “fold” the light curve at the correct period of the pulsar (=put each photon in to the corresponding phase-bin), pulsation shall emerge. Such an analysis can be easily made using an EXEL-type spread-sheet. Thorough this lesson using real satellite data, students learn the concept of “phase” of pulsation/oscillation, and basic statistics.

Search for Black hole candidate on the Galactic plane:

The Ginga satellite, which was operational from 1987 to 1991, carried out many Galactic scan observations to search for new X-ray sources. From the scan profile analysis with several different energy bands, Ginga could determine the accurate position and approximate X-ray energy spectra of the new sources. For example, A new X-ray source was discovered in the Norma region on the Galactic plane in 1988 April ([3]), which is considered to be a black hole candidate because of its characteristic X-ray energy spectrum.

Most X-ray transient sources on the Galactic plane are either neutron star binaries or black hole binaries. One of the big differences is in their energy spectra. Since black holes are more massive than neutron stars and their Schwarzschild radii are larger, the black hole accretion disk inner-radii are also larger than those of neutron stars. Consequently, disk temperature is, in general, lower for black hole candidates than neutron stars.

In this lesson plan, students are given the Ginga Galactic plane scan data and a dedicated program to carry out the scan profile analysis. Students analyze the data, and find out position of the new source, and its energy spectrum. If students compare the energy spectrum of the new black hole candidate and other neutron star sources that are simultaneously observed, they will understand the black hole energy spectrum has lower characteristic temperature.

3. Public Outreach using DARTS

In DARTS, we have been developing systems which are useful for professional scientists to quickly browse a large amount of data, and are also easily used by ordinary people, in particular for science lovers, to take a look at the latest satellite data.

For example, beautiful solar pictures and movies taken by the Yohkoh data (1991-2001) are found at Auroral movies taken by Akebono satellite are at Using JUDO (JAXA’s Universe Data Oriented; one can navigate the universe using mouse by browsing the Suzaku X-ray color pictures.

We have a plan to put explanations for ordinary people to understand the meaning of these satellite data. We would need to cooperate with schools or educational institutes for this project.

References

[1] Yamauchi, S. 2005, “An Ultrasoft Transient X-ray Source in the Norma Region Discovered with Ginga”, Publication of the Astronomical Society Japan, 57, 465