Ohsumi, Japan’s first successful satellite

On February 11, 1970, Ohsumi became Japan’s first successful satellite after it was launched into orbit around Earth. Coming after four failures, it was a considerable achievement of Japanese rocket technology. A.S.Ganesh takes a look at the success story of Ohsumi…

Updated - February 23, 2024 12:53 pm IST

Published - February 11, 2024 12:15 am IST

The Ohsumi satellite.

The Ohsumi satellite. | Photo Credit: JAXA

There’s no doubt that wars create a lot of destruction. It’s been the case throughout recorded history. Wars, however, are also often accompanied by advances at break-neck speed. The fields of science and technology are usually beneficiaries as the advances made without budgetary constraints often contribute to military use that are crucial during the war.

There was unprecedented growth in a number of scientific fields during World War II and its immediate aftermath. The same war, however, also ensured that certain countries fell behind. Japan was one of them.

Terms of surrender

The terms of Japan’s surrender after World War II clearly stated that the country was not allowed to have rocket control technology that could be repurposed for military use. With the available budget also much smaller than those at the disposal of the U.S. and former U.S.S.R, Japan had a mountain to climb when its space exploration began in 1955.

Undeterred, Japan began their journey by conducting Pencil rocket experiments. By 1958, Japan began attempting observations of the atmosphere using a Kappa rocket. In 1962, they set themselves a target of launching a 30 kg satellite in the next five years.

Rapid economic growth

It was in that same year that they switched their launch site to Ohsumi Peninsula, Kagoshima Prefecture. As Lambda rockets were better placed to be equipped with a satellite, they started experimenting with them. With the 1960s seeing Japan’s rapid economic growth, every passing year witnessed rocket performance grow as well.

Illustration shows the configuration of the Ohsumi.

Illustration shows the configuration of the Ohsumi. | Photo Credit: JAXA

The first attempt to launch the L(Lambda)-4S rocket with an Ohsumi satellite (named after the peninsula) failed on September 26, 1966 when the fourth stage attitude control failed. As the fourth stage failed to ignite the next time, the second attempt on December 20 also failed.

Repeated failures

The same failure ensured that the third attempt on April 13, 1967 also ended up as a failure. The fourth launch on September 22, 1969 saw the third stage collide with the fourth stage, thereby leading to a fourth stage control system malfunction. The Japanese media had a field day reporting on the repeated failures. With that, the public too started criticising the programme.

The L-4S-5 loaded on the launcher at Kagoshima Space Center on February 11, 1970.

The L-4S-5 loaded on the launcher at Kagoshima Space Center on February 11, 1970. | Photo Credit: JAXA

It was under such circumstances that the fifth launch attempt was made. At 1:25 p.m. on February 11, 1970, L-4S rocket no. 5 was launched. The rocket was launched successfully and an elliptical orbit was achieved.

Despite the successful launch, there was still tension at the launch site. While they had finally surmounted this challenge, the mission could be termed successful only once the Ohsumi satellite returned over Japanese skies after circling the Earth once.

Detecting the signal

The successful launch on February 11, 1970.

The successful launch on February 11, 1970. | Photo Credit: JAXA

NASA was cooperating with them for tracking the satellite. After the successful launch, NASA’s each successive tracking station reported receiving the signal at Guam, Hawaii, Quito (Ecuador), Santiago (Chile), and Johannesburg (South Africa).

At 3:56:10 p.m., nearly 2.5 hours after the launch, Ohsumi’s signal was received at the Kagoshima Space Center (now called the Uchinoura Space Center after the JAXA space agency was set up in 2003), confirming its first revolution around the Earth. With that, Japan became the fourth country to successfully launch its own satellite, after the former U.S.S.R, the U.S., and France.

The radio signal from Ohsumi grew fainter with every revolution and on the next day, February 12, during its sixth revolution, it was hardly noticeable. During the seventh revolution, 14-15 hours after the launch, the signal was interrupted and could no longer be detected.

Re-entry in 2003

Rapid reduction of power capacity owing to encountering higher than expected temperatures is the reason attributed to losing the signal. But since Ohsumi was inserted into a hyperellipse with a 337 km perigee and a 5,151 km apogee, it could live for a long time.

In fact, Ohsumi went around the Earth for decades, re-entering its atmosphere and burning up only at 05:45 on August 2, 2003. The re-entry location was over North Africa, at the border between Egypt and Libya. Ohsumi’s success turned out to be a guiding light for Japan’s space exploration as it helped them master the gravity turn manoeuvre, paving the way for their future.

0 / 0
Sign in to unlock member-only benefits!
  • Access 10 free stories every month
  • Save stories to read later
  • Access to comment on every story
  • Sign-up/manage your newsletter subscriptions with a single click
  • Get notified by email for early access to discounts & offers on our products
Sign in


Comments have to be in English, and in full sentences. They cannot be abusive or personal. Please abide by our community guidelines for posting your comments.

We have migrated to a new commenting platform. If you are already a registered user of The Hindu and logged in, you may continue to engage with our articles. If you do not have an account please register and login to post comments. Users can access their older comments by logging into their accounts on Vuukle.