An Indian rocket standing 44.4 metres tall and weighing around 320 tonnes is being readied for the country's first commercial satellite launch of 2015.
The rocket will carry five British satellites together weighing around 1,440 kg, said a senior official of Indian Space Research Organisation (ISRO).
"The countdown for July 10 night launch of PSLV-XL (Polar Satellite Launch Vehicle-XL variant) is progressing with butter smoothness. Preparations for filling fuel in the second stage/engine is on. The second stage will be fuelled up on Friday," the official told IANS preferring not to be named.
According to him, the Friday rocket flight will be the first commercial rocket launch for ISRO this calendar year. In terms of number of rocket launches for 2015, it will be second after the launch of navigation satellite-IRNSS-1D earlier in March.
The blast-off is scheduled for 9.58 p.m. on July 10 from the first launch pad at Sriharikota rocket port in Andhra Pradesh, around 80 km from here.
Since 1999 till date, India has launched 40 satellites of other countries with its PSLV rocket and the successful launch of the five British satellites would take the tally to 45.
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The PSLV-XL variant costing around Rs.140 crore is a four-stage/engine rocket with six strap-on motors for additional thrust during the initial phase of the flight.
The first and third stages are powered by solid fuel and are cast ready while the second and fourth stages are powered by liquid fuel which will be filled during the countdown.
The fuelling up of rocket's fourth stage was completed on July 8.
Apart from fuelling up the engines, all the systems would be checked and re-checked during the countdown.
According to ISRO, this is the heaviest commercial luggage carried by a PSLV rocket till date.
Of the five British satellites, three are identical DMC3 optical earth observation satellites weighing 447 kg. These will be put into a 647-km sun-synchronous orbit.
Of the other two satellites, CBNT-1 weighs 91 kg and also is an optical earth observation technology demonstration microsatellite, while the De-OrbitSail weighs 7 kg. This is an experimental nano satellite for demonstration of large thin membrane sail and drag deorbiting.
The total duration - from the rocket's blast off to the fifth satellite separation - will be around 19 minutes 16 seconds.
The three DMC3 and the CBNT-1 satellites are built by Surrey Satellite Technology Ltd. The De-OrbitSail is built by Surrey Space Centre.
According to ISRO, accommodating the three DMC3 satellites each with a height of about three metres within the existing payload fairing or the heat shield of the PSLV was a challenge. Thus, a circular L-adaptor and a triangular Multiple Satellite Adapter-Version 2 (MSA-V2) were newly designed and realised by ISRO for this specific purpose.
France's SPOT 7 satellite weighing 714 kg was the heaviest single foreign satellite carried by a PSLV rocket till now. It was launched on June 30, 2014.
On the other hand, ISRO is also readying for the launch of GSAT6 communication satellite using its heavier rocket Geosynchronous Satellite Launch Vehicle (GSLV).
The GSLV rocket's first stage/engine has been assembled and the activities relating to that rocket assembly are progressing smoothly.
Only after the GSLV rocket launch the testing of a small model of reusable launch vehicle shaped like an aeroplane would be done, an ISRO official told IANS earlier.
Earlier, it was said the test reusable launch vehicle would happen in July 2015.
ISRO officials has told IANS that the test model reusable launch vehicle would be mounted on a strap-on solid booster of PSLV rocket with 9-tonne fuel.
At an altitude of 70 km, the model would get separated and would glide back to earth. The descent speed would be around 2 km per second.
"The descent speed would be controlled through the fins on the machine. In order to protect the equipment from friction heat when it comes back, necessary protective tiles are fixed," the ISRO official had told IANS.
The experimental vehicle would weigh around 1.5 tonne which is a far cry from the actual vehicle that is expected to carry a satellite.
In December 2014, ISRO sent up a 3.7 tonne giant cup cake shaped module - called Crew Module Atmospheric Re-entry Experiment - to study its re-entry characteristics, aero-braking and validation of its end-to-end parachute system.
A 630-tonne rocket went up to 126 km when the crew capsule got detached and fell into the Bay of Bengal, 20 minutes after the blast off.
The descent speed of the crew module was controlled by three parachutes.
However, the aircraft shaped vehicle will not have any parachutes to control the descent speed but the fins and other parts would do so.