Changes made to ISRO GSLV-D5's CUS and FBTP since GSLV-D3's LH2/LOX CUS failure to sustain ignition?

Question

The launch of the ISRO GSLV-D5 launching India's GSAT 14 advanced communications satellite (weighing 1,980 kg) is slated for 19th of August, 2013, flying in the GSLV Mk.2 configuration with an Indian-built cryogenic third stage (LH2/LOX propellants). This mission is delayed from October, December, January, February, April, July and Aug. 6.

The 2010 GSLV-D3 mission failed due to the Cryogenic Upper Stage (CUS) not sustaining ignition for longer than 0.8 seconds after initial burn and the subsequent failure of the fuel booster turbo pump (FBTP):

GSLV-D3 was launched from the Second Launch Pad (SLP) at Satish Dhawan Space Centre SHAR, Sriharikota on April 15, 2010. Flight testing of the Indigenous Cryogenic Stage was unsuccessful.

                            

                            ^{GSLV-D3 Cryogenic Upper Stage (CUS) (Quote and photograph source: ISRO)}

According to The Hindu:

There is enormous focus on this mission, as the GSLV flight with an indigenous cryogenic engine failed in April 2010. The subsequent GSLV flight with a Russian cryogenic stage also failed in December of that year.

...

In April 2010, the indigenous cryogenic engine ignited; the steering engine and the gas generator ignited, but the ignition could not be sustained beyond 800 milliseconds and the fuel booster turbo pump (FBTP) stopped.

       

         ^{Various ISRO launch vehicles. The configuration to be launched on Aug. 19th is GSLV-Mk II with the indigenous Cryogenic
         Upper Stage (CUS) using LH2/LOX propellants as the 3rd stage (in black just below the payload) (Image: ISRO).}

S. Ramakrishnan, Director of Vikram Sarabhai Space Centre (VSSC) in Thiruvananthapuram, brimmed with confidence when asked whether the indigenous cryogenic engine would perform well this time.

...

“Of course,” he said. “We are doing well. We have done all the possible tests. As of now, the [cryogenic] stage health is fine. All checks show that the health of the vehicle is all right.”

...

Dr. Radhakrishnan elaborated on the steps taken to address the inadequacies of the 2010 flight. He said, “Over the last three years… we have done a series of ground tests on the sub-systems and the cryogenic engine” at the LPSC at Mahendragiri, Tamil Nadu, “after making the necessary design changes in the FBTP and the oxidiser turbo pump.” An important test done this year was testing the FBTP in operating conditions at cryogenic temperatures. Ignition of the engine in high-altitude conditions [simulating the vacuum in space] was also done. The duration of this test was 3.5 seconds, when the ignition of the main engine, the gas generator and the two steering engines should take place in a given sequence. “This happened.”

^{All quoted excerpts except the first one copyright and courtesy of: The Hindu}

    

     ^{The indigenously built cryogenic engine being tested at the High Altitude Test Facility (HAT) of the Liquid Propulsion Systems
     Centre (LPSC), Mahendragiri in early 2013. (Photograph source: ISRO on Facebook)}

My questions are:

• Precisely which additional ground tests were conducted on CUS since the GSLV-D3 for the planned GSLV-D5 launch (short of those already described in the excerpt),
• what changes were made to its design to support this apparent confidence of Dr. Radhakrishnan, Director of VSSC in Thiruvananthapuram that the GSLV-D5 will complete its mission successfully (looking for more detailed explanation),
• how precise are high-altitude tests to test performance in near vacuum conditions (any previous references?), and
• what does “testing the FBTP in operating conditions at cryogenic temperatures” involve?

In a nutshell, I expect answers to further substantiate the claims and confidence that the future GSLV-D5 mission will "deliver" (no pun intended) with a bit more detail than the linked to news article in The Hindu.

Primary focus should be on the reliability analysis of Cryogenic Upper Stage and its components (e.g. FBTP). Somewhat liberal interpretation of any test data provided and comments are not discouraged, if there isn't any other way, but please provide a link to your sources for reference.

Answer 1

The closest I could find to information on this came from this brochure:

Design Improvements in GSLV-D5

Based on its performance during the earlier missions, end-to-end design of GSLV as well as indigenous cryogenic stage systems have been re-examined. Design modifications are implemented wherever required along with rigorous ground testing and improvements are made with respect to the fabrication and quality control to enhance the reliability

• The changes that were made:

• Redesign of Lower Shroud which protects the cryogenic engine during atmospheric flight of GSLV-D5
• Redesign of the wire tunnel of the cryo stage to withstand larger forces during flight
• Revised Aerodynamic characterisation of the entire launch vehicle
• Inclusion of Video Imaging System to monitor lower shroud movement during various phases of flight
• Improvements in the Cryogenic upper Stage:
• • Modified design of the Fuel Booster Turbo Pump (FBTP), taking care of the expansion and contraction of the bearings and casing at cryogenic temperatures
• • Modification of Ignition Sequence to ensure the smooth, successful and sustained ignition for Main Engine (ME), Steering Engine (SE) and Gas Generator (GG)

In addition, indigenisation of many critical systems including Liquid Hydrogen Propellant Acquistion System (to prevent the possibility of contamination), Polyimide pipelines and Liquid Oxygen & Liquid Hydrogen Level Sensors has been successfully accomplished.

• Ground tests performed:

In order to validate the design improvements, the following extensive qualification tests have been carried out on the engine at the Main Engine Test (MET) facility and the High Altitude Test (HAT) facility:

• Two acceptance tests for flight unit of FBTP
• High altitude tests to confirm the ignition sequence in flight under vacuum
• Cryogenic Main Engine (200 sec) and Steering Engine (100 sec) acceptance tests

All the improvements have been thoroughly reviewed by expert committees including eminent national experts.

That's really all I could find on the subject. Of course, the launch was called off due to a fuel leak and delayed until December, so more info may come with time.