ASM
Inside Razaksat
Sometime in the next few months, Malaysia will finally launch its Razaksat-1 satellite, its first attempt at an Earth observation vehicle join up. At least it will if plans go according to schedule.
It’s a big ‘if’. The satellite is already three years late (and counting). The original plan was to launch the satellite in 2005, but that was delayed due to problems with the launch vehicle and with the satellite itself.
Last year, there were plans to celebrate the 50th Independence Day on 31 August 2007 with a space flight. There were good reasons for deciding on such a symbolic date. Apart from the need to get the long anticipated satellite into orbit as soon as possible, space technology represents part of the political vision in Malaysia. The government has committed to making the country a member of the developed world by 2020.
To do that, nurturing its science and engineering expertise is essential.
But there is many a slip t’wixt cup and lip. Malaysia’s Science, Technology and Innovation Minister Datuk Seri Dr Jamaludin Jarjis told a conference early in 2007 that the government had signed off on a private American-based company, SpaceX, to undertake the launch.
But that launch was cancelled. Now the launch is set for early in the second quarter of 2008.
| The Razaksat satellite will be launched on a radical new rocket. |
Under the plan agreed by Minister Jarjis, Razaksat will be launched from Omelek Island, one of the Marshall Islands, using the SpaceX Falcon 1 launch vehicle.
But it’s the launch vehicle that is the problem. Falcon is the first practical orbital delivery system funded entirely by private money. SpaceX is a space transportation startup company, founded by PayPal’s founder Elon Musk to provide commercial launch-to-space services.
Musk is, of course, a master of spin. In fact, the program to date has largely been funded by the Pentagon. The development of the Falcon was indeed privately funded, but the Department of Defence paid for the first two test flights – in 2006 and 2007 – under a program that evaluates new US-built launch vehicles.
Both payloads were funded by the Defence Advanced Research Projects Agency (DARPA).
Neither of these payloads achieved orbit. However, according to SpaceX publicity, the second test launch was largely successful. As a result, SpaceX declared Falcon 1 fully operational. First client: Malaysia.
None of this will matter if the launch is successful. The great beauty of the Falcon is that it is cheap. Most sources agree the Malaysians are paying around $7 million for the flight, although the Malaysian government has not confirmed that figure. If it can be made to work, it will revolutionise the economics of getting small payloads into space.
The government owned ATSB is the prime contractor on Razaksat-1. It is the second satellite produced by ATSB for the Malaysian government. The first, Tiungsat-1, was launched in 2000.
The Razaksat program has cost the Malaysians RM60 million (about $17 million).
According to the country’s Deputy Science, Technology and Innovation Minister, Datuk Kong Cho Ha, the same satellite would have cost ten times more if it had been imported from another country.
Razaksat started life as MACSat (Medium-sized Aperture Camera Satellite), a joint development program between Astronautic Technology and Satrec Initiative Co. in South Korea. Satrec took responsibility for the optical payload.
The program started at the end of 2001, with the aim of completing the development by the end of 2003. The satellite was eventually delivered late in 2006.
There is much that is noteworthy in the Razaksat project. At 150 kg, it will offer 2.5 metre resolution in its pan mode, about the same as Spot-5, but at a tenth of the price and mass.
It is an example of the impact of highly integrated electronics on satellite design.
Even more interesting, Razaksat will be placed into a novel orbit – it will be inclined only nine degrees to the equator.
Normally, remote sensing satellites orbit near 90 degrees. This way, the satellite flies over every spot on Earth sooner or later. However, the time between visits is measured in days.
Razaksat will only see the equatorial regions, but it will see them often. Its orbit will bring it within sight of any given point every 100 minutes or so – although it may not be possible to get a nadir view of regions near 9 degrees north or south for up to 25 days. Even so, its orbit will carry it over some portion of Malaysia 14 times a day.
Speaking during a recent space conference in Kuala Lumpur, Norhizam Hamzah from ATSB said the aim is to optimise the potential for optical remote sensing in what is a very cloudy part of the world. They estimate that any given point under the Razaksat orbit will be obscured by cloud about 80 per cent of the time. The orbit will allow them to exploit the other 20 per cent.
This does not happen in classic remote sensing satellite orbits, so it can be months, even years, between the coincidence of a cloudless scene in the equatorial regions and an available satellite.
The MAC instrument is a pushbroom camera with five linear detectors (one panchromatic, four multi-spectral). The pan sensor will – at the nominal 685 kilometre orbital altitude – give 2.5 metre resolution. The MSS will give 5 metres. It will be possible to pan-sharpen the MSS imagery to generate 2.5 metre colour. Each pixel will be 8 bits deep. The swath will be about 20 kilometres wide.
The satellite can store up to store up to 30 Gbit/s on board, which is equivalent to a 20 x 600 km strip. The satellite will be able to tilt 30 degrees across track.
To download this data, the satellite will be heavily dependent on an X-band communications link that can transfer data at 30 Mbit/s. There are also a number of other channels available with speeds of 9600 bit/s, 1200 bit/s and 38.4 kbit/s. However, these are intended for control and communications telemetry only.
Given the height of its orbit, Razaksat will be in contact with controllers for about 500 seconds every orbit. This implies a download of about 11 Gbit/s each orbit on the X band link – for a nominal scene size of 20 x 200 km.
Operations will be conducted at the mission control ground station run by the Malaysian National Space Agency (Ankasa) in Banting, Selangor.
Ankasa will provide four levels of Radarsat products. Level 0 products will be radiometrically corrected, level 1 systematically corrected, level 2 precision corrected and level 3 ortho-rectified. Radiometric correction removes radiometric errors and distortion. Systematic, precision and ortho-rectification correction successively remove more and more geometric distortion.
Processing for level 0 and 1 is based on ancillary data transmitted from the satellite or built into the processing system. Level 2 and 3 products will be corrected with Ground Control Points and a digital elevation model.
Given the constraints of the orbit, ATSB is anxious to reach as many users as possible in equatorial countries. ATSB made an announcement of opportunities in mid-2007, under which it will co-operate with researchers – both inside and outside Malaysia – to develop applications for Razaksat data.
It will be interesting to observe users’ reaction to this spacecraft, the first designed explicitly for equatorial remote sensing. The other method of combating cloud, of course, is to use radar.
In 2008, two high resolution radar satellites – Radarsat-2 and TerraSAR-X – will become available to users. They both have a nominal one metre spatial resolution mode, and both are intended for the same users served by optical satellites.
