At first the astronaut was charged with attempted kidnapping and other counts. Then prosecutors upped the charge to attempted murder, basing it on the weapons and other items they said police had found with Nowak or in her car: pepper spray, a BB-gun, a new steel mallet, knife and rubber tubing.
Nowak, a 43-year-old Navy Captain and married mother of three, was released from jail on $25,500 bail and ordered to wear a monitoring device.
Her lawyer, Donald Lykkebak, took issue with the most serious charges.
"In the imaginations of the police officers, they extend these facts out into areas where the facts can't be supported," Lykkebak said.
"The intent was there to do serious bodily injury or death," said Orlando Police Sgt. Barb Jones, referring to the items found in Nowak's car.
NASA put Nowak on a 30-day leave and removed her from mission duties. Agency spokesman John Ira Petty at Johnson Space Center in Houston said he was concerned about the people involved and their families. But, he added, "We try not to concern ourselves with our employees' personal lives."
If convicted of attempted murder, she faces between 30 years and life in prison, authorities said.
"It looks like it was a fairly elaborate plan, and we believe that she was probably going to try to kidnap the victim and, you know, possibly do serious bodily harm," Sgt. Jones told Jessica D'Onofrio of CBS affiliate WKMG-TV.
Chief astronaut Steve Lindsey, who flew with Nowak to the international space station last July aboard space shuttle Discovery, and fellow astronaut Chris Ferguson attended the earlier hearing.
"Our primary concern is her health and well-being and that she get through this," Lindsey told reporters later. "Her status (with the astronaut corps) has not changed."
Ferguson said he was "perplexed" by Nowak's alleged actions.
Police said Nowak drove 900 miles, donned a disguise and was armed with a BB gun and pepper spray when she confronted a woman she believed was a competitor for the affections of Navy Cmdr. William Oefelein, an unmarried fellow astronaut.
Oefelein, 41, piloted the space shuttle Discovery in December. He and Nowak trained together but never flew a mission together.
Nowak told police that her relationship with Oefelein was "more than a working relationship but less than a romantic relationship," according to an arrest affidavit.
Inside Nowak's vehicle, which was parked at a nearby motel, authorities found a pepper spray package, an unused BB-gun cartridge, latex gloves and e-mails between Oefelein and Colleen Shipman.
They also found a letter "that indicated how much Mrs. Nowak loved Mr. Oefelein" and Shipman's home address, the arrest affidavit said.
Police said Nowak told them that she only wanted to scare Shipman into talking to her about her relationship and didn't want to harm her.
"If you were just going to talk to someone, I don't know that you would need a wig, a trench coat, an air cartridge BB gun and pepper spray," Jones said. "It's just really a very sad case."