By Christiana Adegbaju
Satellite imagery describes the images [pictorial representation] obtained from remote sensors onboard a satellite in a space without any direct physical contact with object being viewed or captured. The images are captured, stored, selected, analyzed, processed and distributed to users in continuous form to aid prompt response and plan mitigation measures to prevent or manage air disaster in future. Unfortunately, satellite imagery has not been fully utilized in disaster prevention and post-disaster monitoring in Nigeria.
Month or years following an air disaster, updates on the status of the affected crash site can be obtained by a single image to identify if such areas has fully recovered or is recovering from the unfortunate incident.
Timeline of Air Disasters in Nigeria
Air disasters are unwanted events as their occurrence result in colossal loss of lives, properties and money [insurance and compensation]. The negative impacts of such disasters are still felt month and even years after such events, sometimes leading to foreclosure of companies [ for example Bellview Airlines],emotional trauma of victims or possible deaths of relatives [a female parent who lost her three children in Sosoliso air crash eventually died years later]. Usually air disasters occurs as a result of human error, bad weather conditions, old air craft, and equipment failure. Although these disasters can be avoided if preventive measure are put in place and adhered to, a total occurrence cannot be eliminated. Therefore, efforts should be made to reduce to the barest minimum of losses arising from air crash by timely response in terms of search and rescue activities and post event reliefs.
In Nigeria, air crashes have been a bane of the aviation industry. It has been found out there is usually delayed response when such event happen due to the inaccessibilityof the crash site, undetermined location, blockage of access routes, and ineffective communication. Also, there is always a prolonged delay in the procedure for victim to get adequate compensation and estimation of losses, affected properties, and extent of damage usually proves difficult. An example is the case of a pastor who loss properties worth millions of Naira in the Dana air crash and who is still claiming that he is yet to be fully compensated.
The applications of satellite images and pictures are search and rescue operations; weather mapping and conditions; better mapped air routes and safety areas; determination of obstacle’s coordinates [height, attitude and distance]; air disaster prevention; and high information content data to be used by disaster monitoring and aviation agencies for relief, emergency and air safety purposes.
Sensor Requirement for Quality Images
The fundamental requirements for quality images are; a] high resolution imaging capability; b] timely global imaging access; c] high data throughput; d] support a number of special imaging modes; e] provide high accuracy geo-location knowledge of the imagery acquired; f] fast response; g] contains multi-temporal scenes to also illustrate the progression of recovery; h] functional spatial resolution [ detail discernible in an image]; and I] good area coverage [swath width and revisit period].
The prime data requirement is for high information content and a balance between resolution and data handling ability. Processed should be available moments after imagery acquisition.
Nigeria’s Earth Observation Satellites
Nigeria has two earth observation satellites in place –Nigeria Sat II and SAT X [N2 and NX] which are part of the Disaster Monitoring Constellation System [DMCS] as well as one Communications Satellite, NigComSat 1R -Africa’s first communications satellite. Their efficient applications in conjunction with other DMCS and communication satellite will contribute to good quality and high resolution images, precise location coordinates and effective communication links necessary for disaster monitoring and information gathering. Their use will also reduce costs of obtaining or buying images from external sources.
NigeriaSat-2 and Sat-X are earth observation satellites, NigeriaSat-2 being the first satellite in the African Resources Management [A R M] constellation. Both satellites operate in the LEO, Sun-synchronous near-circular orbit, with an inclination of 98.25, an orbital period of about 98 minutes and temporal resolution of four days.
Both N2 and SAT X have cameras on them with resolving power of 2.5 meters [panchromatic resolution, black and white mode], sensitive to 5-metre multispectral [NIR red, green and red bands of electromagnetic radiation region equivalent, to Landsat TM bands 2.3and 4], and 32-metre multispectral [medium resolution, NIR red, green and red bands].
Images are stored in 1-gigabyte solid-state data recorder and returned via an 8-Mbit/s S-band downlink. In the event of disasters, NigeriaSat-2 complements its fellow Disaster Monitoring Constellation satellite by using its high resolution imager to ‘zoom in’ on areas of interest and determine if individual buildings are damaged, bridges destroyed or road impassable. This enable rescue operatives and security personnel to determine best possible means of douse fires, establish communication links especially if terrestrial links are grounded, reach and evacuate victims to nearest medicals centers, seal disaster scene from public evacuate wreckage know if victims are affected too.
Disaster Monitoring Constellation [DMC]
The Disaster Monitoring Constellation consist of earth observation satellites of the partnership countries namely Algeria, China, Nigeria, Turkey and United Kingdom. The satellites are arranged in constellation to provide a global coverage and daily-revisit with the provision of real-time data to monitor fast changing phenomena on the Earth’s surface. The DMC initiative is a contribution to the global efforts in disaster management. In conjunction with CEOS [Committee on Earth Observation Satellites] and GEOSS [Global Earth Observation System of Systems], the world has adequate satellites to cover the whole world and monitor various disaster activities globally.
There is a clear evidence of limited use of imagery for efficient monitoring of disaster and post evaluation in Nigeria. Most images available are pictures taken by hand held cameras of personnel around crash sites. There need to be a paradigm shift by users towards the use of satellite imagery augmented with aerial photography (manned or unmanned) for wider area coverage, real time information, timely response, location determination, mitigation measures and hazard assessment. Also, the processed data offers a better insight and provide a range of information to either prevent these events, or use the post data to provide adequate compensation and relief measures.