Here's all you need to know about the Indian Space Research Organisation's mission to launch 20 satellites in one rocket.

Gearing up for the mission to launch 20 satellites in a single rocket on Wednesday, the Indian Space Research Organisation (ISRO) on Monday commenced the 48-hour countdown for the launch of PSLV C-34 rocket. It will lift off from the Satish Dhawan Space Centre at Sriharikota at 9.25 a.m. on June 22.

The countdown exercise encompasses spacecraft health checks and preparations for propellant filling operation of second stage (PS2) of PSLV-C34 are in progress.

So what happens during Wednesday's launch?

ISRO on Wednesday would launch into orbit 20 satellites in one go through its PSLV C-34 rocket. In about 26 minutes after the rocket takes off from the second pad of the Satish Dhawan Space Centre at Sriharikota at the scheduled time of 9.25 am, all 20 satellites would be launched into intended orbit. The first satellite would be injected into orbit after 16 minutes and eventually the remaining 19 satellites would be placed into orbit in the next 10 minutes.

The PSLV-C34 on on the Second Launch Pad. Photo: ISRO The PSLV-C34 on on the Second Launch Pad. Photo: ISRO

Here are some of the satellites that would be launched on Wednesday

According to ISRO, the total weight of all the 20 satellites is about 1,288 kg.

The co-passengers include satellites from the US, Canada, Germany and Indonesia as well as two satellites from Indian Universities.

Cartosat-2 series satellite

The primary satellite to be carried by PSLV C-34 rocket is similar to Cartosat-2, 2A and 2B satellites launched earlier. The imagery to be sent by the satellite would be useful for cartographic applications, coastal land use and regulation, utility management like road networking, water distribution, creation of land use maps, precision study, change detection to bring out geographical and manmade features and various other Land Information System and Geographical Information System applications.

Mass: 727.5 kg

LAPAN-A3 (Indonesia)

The microsatellite is for Earth observation and is intended to be used to monitor land use, natural resource and environment.

Mass: 120 kg

M3MSat (Canada)

Maritime Monitoring and Messaging Micro-Satellite is a technology demonstrator mission jointly funded and managed by Defense Research and Development Canada (DRDC) and the Canadian Space Agency (CSA). The satellite’s primary mission is to collect and study Automatic Identification System signals from low-Earth orbit.

Mass: 85 kg

The Fully integrated PSLV-C34 with all the 20 Spacecrafts being moved to second launch pad (SLP). Photo: ISRO The Fully integrated PSLV-C34 with all the 20 Spacecrafts being moved to second launch pad (SLP). Photo: ISRO

GHGSat-D (Canada)

Built by Space Flight Laboratory of the University of Toronto Institute for Aerospace Studies, the Earth observation satellite is meant for measuring the atmospheric concentration of greenhouse gases (Carbon Dioxide and Methane).

Mass: 25.5 kg

BIROS (Germany)

Berlin Infrared Optical System (BIROS) is a small scientific satellite from the German Aerospace Center and its mission objective is the remote sensing of high temperature events.

Mass: 130 kg

SkySat Gen2-1 (U.S.)

Designed and built by Terra Bella, a Google company based in Mountain View, California in the U.S., the small Earth imaging satellite is capable of capturing sub-meter resolution imagery and HD video.

Mass: 110 kg

PSLV-C34 first stage integration in progress. Photo: ISRO PSLV-C34 first stage integration in progress. Photo: ISRO

Dove Satellites (U.S.)

A total of 12 Flock-2P Earth imaging satellites are to be launched in this mission. They would be packed in three dispensers.

Mass: 4.7 kg each

Sathyabamasat (Sathyabama University, Chennai)

The satellite aims to collect data on green house gases.

Mass: 1.5 kg

Swayam (College of Engineering, Pune)

The satellite aims to provide point to point messaging services to the HAM (amateur radio) community.

Mass: 1 kg

Has the ISRO launched these many satellites earlier?

No. The record that ISRO has held so far was launching 10 satellites in 2008. ISRO’s PSLV-C9 rocket launched a Remote Sensing satellite CARTOSAT-2A along with Indian Mini Satellite (IMS-1) and eight nanosatellites on April 28, 2008.

Have space agencies from other countries carried so many satellites in one go?

Yes. In 2014, Russia had launched 37 satellites in one go. The U.S. had launched 30 satellites in one go.

Which countries’ satellites have been launched by ISRO so far?

So far, ISRO has launched satellites for Algeria, Argentina, Austria, Belgium, Canada, Denmark, France, Germany, Indonesia, Israel, Italy, Japan, Korea, Luxembourg, Singapore, Switzerland, The Netherlands, Turkey, United Kingdom and the United States of America.