Sun Ra didn't come to Philadelphia for the cheesesteaks. The space jazz innovator moved from New York to Germantown in the 1960s for the benefit of humankind. "To save the planet, I had to go to the worst spot on earth, and that was Philadelphia, which was death's headquarters." Thank you, Sun, for keeping the earth alive. In repayment, the Ars Nova workshop will tonight stage a tribute called In Death's Headquarters: In Celebration of Le Sony'r Ra on the cusp of the closing of the Institute of Contemporary Art's Pathways To Unknown Worlds exhibit on the University of Pennsylvania campus. It features 12 member Philadelphia ensemble Sonic Liberation Front, who will premier a piece called "Jetway Confidential No. 3 (for Sun Ra)" as well as Ra's own "Where Pathways Meet." The SLF will be joined by Planet Y, the duo of Stinking Lizaveta guitarist Yanni Papadopoulos and Charles Cohen, who plays a synthesizer like device called the Buchla music easel. Performance films of Ra, who moved on from Philadelphia (and Saturn) to death's headquarters for real, in 1993, will be projected on the walls. The show starts at 7, and it's free, as is the Pathway To Unknown World show, which ends its run on Sunday.