ISRO Rocket to Launch ESA Probe - Proba 3

In the afternoon of December 5, a PSLV-XL rocket will thunder off the pad from Satish Dhawan Space Center carrying two of the European Space Agency’s (ESA) probes. The mission is named Proba-3, a precision formation flying mission.

A PSLV-XL rocket lifts off from Satish Dhawan. Credit: ISRO

The PSLV-XL Rocket

The PSLV is a workhorse rocket for India’s space program. 59 times since its debut in 1993, 57 of which successfully, the Polar Satellite Launch Vehicle has proven itself to be reliable while launching about 3 times per year.

A PSLV-XL rocket is being transported to the launch pad. Credit: ISRO

The variant of the PSLV being used for this mission, the -XL, is the most powerful variant ISRO has to offer. The XL could deliver a 4.2 ton payload to a Low Earth Orbit, using a standard 200 kilometer 30 degree orbit as a reference.

The -XL uses 6 S12 solid motors which each produce 703.5 kN of thrust, putting the total motor thrust to about 4,221 kN at liftoff. The boosters run for 70 seconds burning HTPB.

The first stage uses a single S139 motor that runs on HTPB and has a thrust of 4846.9 kN. The first stage burns for 110 seconds.

Unlike the first stage & boosters, the second stage uses liquid fuel. The second stage, powered by 1 Vikas engine, runs on Dinitrogen Tetroxide (N2O4) and Unsymmetrical dimethylhydrazine (UDMH).

The third stage runs on HTPB for 113.5 seconds and provides a thrust of 250 kN.

The fourth stage will insert the twin probes into their desired orbit, using two L-2-5 engines that run on MMH (Monomethylhydrazine)/MON (Mixed oxides of nitrogen).

The fourth stage is depicted in this render by the ESA, showing the two Proba-3 spacecrafts separating.

The Proba-3 Probes

The two probes aim to prove formation flying technologies and conduct some rendezvous experiments. The PSLV-XL rocket will insert them into a highly elliptical 600 x 60,530 kilometer orbit at 59 degrees.

The two spacecraft each have different names. One is named the Occulter spacecraft, and the other is the Coronagraph spacecraft. While they are flying 150 meters apart, the Occulter will cast a shadow on the Coronagraph spacecraft which causes an eclipse. The Coronagraph spacecraft will then be able to study the Sun’s corona for up to 6 hours per orbit.

The Occulter casts a shadow on the Coronagraph. Credit: ESA

The Proba-3 probes will study and answer many mysteries & questions we have about our sun, space weather, and the radiation belts. They will test formation flying to the precision of millimeters.