Longtime Cambridge resident Maria Joubert used to weather the coldest nights of the winter at the Harvard Square Homeless Shelter on Winthrop Street.

But two years ago, Joubert and her husband Rick responded to an item in a local weekly newspaper advertising

a five-month-old half-Chihuahua, half-terrier, whom they named Becky. Joubert refuses to leave Becky alone in the couple’s gray Volvo station wagon, and the shelter—run by Harvard students and housed at the University Lutheran (UniLu) Church—maintains a strict no-dogs-allowed policy.

For Joubert, who speaks disdainfully of the “crackheads and druggies” that she says populate UniLu, the move to living full-time in the station wagon was a small sacrifice to make for her canine companion.

Joubert and Rick (who declined to provide his last name) say they subsist day-to-day on a diet of free dinners from local churches and charities. They say they earn enough from their federal Supplemental Security Income (SSI) check to afford coffee and tea—and an occasional danish—in the mornings. For lunch, Rick sometimes cashes in cans and bottles to buy a whole chicken from the DeMoulas Market Basket in Somerville for $4.59.

Their hand-to-mouth existence is not uncommon in Cambridge, despite the last Census estimate that the city’s median family income is nearly $60,000 a year.

When the Class of 2005 emerges from Johnston Gate today, the graduates will inevitably encounter the now-familiar sight of panhandlers lining Mass. Ave.

But if city officials meet their declared goals, the Class of 2015 will march in cap and gown to a Square where homelessness is a thing of the past.

Last month, a committee chaired by Mayor Michael A. Sullivan released its “Ten-Year Plan to End Homelessness in Cambridge,” which comes on the heels of a Bush administration pledge to eliminate “chronic homelessness” nationwide by 2013.

But Joubert and her friends, gathered for a recent dinner at the Christ Church on Garden Street, scoffed at those quixotic aims.

“That’s never going to happen,” says John Kaye, a sporadically-employed painter from Brighton, echoing the sentiments of Harvard experts and even some Cambridge officials.

Several seemingly insurmountable obstacles lie in the city’s path. Local real estate prices are skyrocketing, while federal housing aid to Cambridge decreased last year. The federal government’s limited definition of “chronically homeless” prevents some Cantabrigians from accessing the help they need. And poor individuals continually flock here from across the Greater Boston area, attracted by the perception that students, tourists, and affluent Harvard Square residents drop generous donations in panhandlers’ cups.

TAKING AIM

One night last January, just 48 hours after a blizzard, Cambridge officials counted 501 homeless people living in the city. Forty-one were living on the street—like Joubert and Rick, who were bundled up beneath blankets in their station wagon.

Four months later, the city released a plan designed to ensure that low-income Cantabrigians aren’t left out in the cold.