John David Mangus, 91, passed away peacefully on August 13, 2026, at his idyllic home on Brown Run Road, surrounded by family and friends, with the sound of the stream in the background. John was predeceased by his beloved wife, Louise; daughter, Juliana; son, Nicholas; and two siblings, Mary and Nicholas. He is survived by his sister, Collette; sons, David (Sand) and Paul (Trish); daughter-in-law, Margee; grandchildren, Nicholas, Anthony, Laura, Victoria, Francesca, and Alexandra; and great-grandchildren, Riccardo, Miles, Luna, Sloane, and Sidney.

Born on September 17, 1934, at Warren General Hospital, John was raised in Warren, where he excelled academically and was awarded the M.V. Ball Science Prize at his high school graduation. He went on to earn a Bachelor of Science degree in mathematics, with minors in chemistry and philosophy, from Gannon University in 1956, where he was also awarded the Gannon Science Prize.

John met the love of his life, Louise McCandlish, in Frederick, Maryland while he was an army draftee working at Fort Detrick and she was working at nearby Hood College. They exchanged marital vows at St. John’s Church on June 14, 1958. The following year they moved to State College, Pennsylvania, where John earned his Master of Science degree in physics, with a minor in mathematics, from Penn State. John was then hired by NASA and they moved to Berwyn Heights, Maryland in 1962. There John was active at his church where he was a lector, taught marriage classes to 12th grade CCD students, and played the mandolin in a folk group during mass.

At NASA John quickly rose through the ranks and was appointed Head of the Optics, Electrochemical, and Plastics Branch at Goddard Space Flight Center. As an optical physicist with expertise in solar physics and space astronomy, John demonstrated a keen intellectual passion and exacting professional focus on the scientific exploration of light. He worked on many ground-breaking missions that contributed to major break-throughs in scientific knowledge about the Earth and the Universe. Here we mention four foundational missions about which he was most passionate.

Voyagers 1 & 2. John’s team built the instruments for the first probes to capture detailed images of our solar system planets and the magnetic field beyond our solar system.

Cosmic Background Explorer. John’s team was the first to create spacecraft telescopes that mapped the first light from the Big Bang, confirming the age of our universe to be 13.8 billion years old.

Hubble Space Telescope. When Hubble was launched on April 24, 1990, it produced fuzzy images. John quickly found what was wrong and developed a fix for all of the new instruments. He was also responsible for constructing the technical case for the Department of Justice to sue the contractor for their mistake and coverup.

James Webb Space Telescope. John was the senior optical advisor responsible for overseeing and creating new, technically challenging instruments capable of high precision imaging. He continued this work as an essential consultant well into his retirement. The successful launch on December 25, 2021, marked the start of a new era of scientific exploration, enhancing our understanding of the young universe with greater clarity than ever before. This was the capstone of John’s amazing career.

On the way to becoming a world-renowned optical physicist, John earned numerous awards, contributed to the work of professional societies, built strong international relationships, and developed Goddard’s optics branch into the world’s premier optics facility. John received two Goddard Exceptional Performance Awards, in 1971 and 1982.

He was appointed to numerous NASA Headquarters and International Review Committees and published many papers in peered reviewed journals and technical proceedings. He was also appointed to the Optical Society of America’s Optics and Photonics News publication editorial advisory board. These activities brought him into contact with every major scientific investigator in the field of optics at academic institutions in this country and abroad in Europe, Japan, Australia and Canada. John was also awarded the NASA medal for Outstanding Leadership in “recognition of his outstanding leadership in the development of a space optics capability for NASA.”

John retired from NASA in 1994 and returned to Warren where he and Louise rebuilt his ancestral family home. There he enjoyed hunting, fishing, and bee-keeping. In addition to his ongoing consultation with NASA during retirement, John was deeply committed to his community and devoted valuable time serving multiple clubs and organizations. Warren County Hospice was especially important to him and he served as membership chairman and treasurer of the Advisory Board for many years. Ever the historian, he served as Warren County Historical Society Board of Directors President. He was Secretary of the Conewango Club at the time of the building fire and renovation. Additionally, John supported the Struthers Library Theater and served on the Warren County Concert Association Board of Directors.

One of the highlights of John’s retirement was his involvement with the Shakespeare

Club of Warren, which provided opportunity for inspired creativity with like-minded lovers of the bard. Little known fact: during the congressional investigation into the Hubble Telescope, John could be heard roaming the house muttering, “Hubble, Hubble, toil and trouble…”

John strongly valued encouraging scientific education. He happily presented science lectures at Beaty Middle School, Gannon University, the Rotary Club, Warren County Hospice Volunteers, the Woman’s Club, the Kiwanis Club, and Martz Observatory.

He was passionate about participating in the Beaty Middle School October Sky Rocket Launch Day. Further, John and Louise established a scholarship fund for Warren students who major in science or medical-related fields at Gannon University.

Aside from his extraordinary career and community accomplishments, John was the epitome of the devoted husband. Louise unfortunately suffered a long-term illness that required exceptional care-taking. John navigated through tragedy with conscious intention and unwavering love, revering life and ultimately facilitating soulful, precious passage. We are all blessed to have known him and can only hope to live up to his example.

Family will receive friends on Friday, August 21, 2026, at the Donald E. Lewis Funeral Home, Inc., 304 East Street, Warren, PA., from 6 to 8 P.M. A private interment will be held at the convenience of the family at St. Joseph R.C. Cemetery, Warren, PA.

E-mail condolences may be sent by visiting www.lewisfuneralhomeinc.com., or on the funeral home Facebook page. In lieu of flowers. please make donations to Hospice of Warren County, 1 Main Avenue, Warren, PA. 16365. www.hospiceofwarrencounty.org.