Phenomenology is based on a belief that it is a science
Simplified definition of phenomenology is that phenomenology represents study of the phenomena that appear in a mind. Basic belief of phenomenology is that we could somehow classify these phenomena, and that individual experience and consciousness of one mind (one person) is based on some underlying universal principles.
One famous example of phenomenological problem is What Is it Like to Be a Bat?. In an essence, is there anything that could connect experiences of a bat and of a man, even if they exists in a same space and time ? And if not a bat, then at least two different human beings - do they experience same thing when they look at the same red wall ? Phenomenology holds as axiom that these two experiences, while not the same, are formed on the same basis. For example, seeing red wall is distinctly sensory experience, different then thinking about red wall, and also different from having emotional experience triggered by red wall.
If then we accept this basic premise about classifying phenomena in different groups and sub-groups, then classical scientific relations and sentences would appear in the form group A has(or has not) a property B. For example, robots have no feelings (feelings are not phenomena that robots could experience) . Statements like this, of course, form any scientific theory.
Now that we have scientific theory, next step would be to objectively proof it. Phenomenology could not perform completely impersonal experiments like for example physics, but it could have test-subjects, in a manner of psychological experiments or social studies. In or example with robots, we could try to prove that robots behave the same no matter if their operator curses or praise them.
Finally, with the set of proven (and disproven) statements, and methodology how to do this, phenomenology would classify as a science in a formal manner. But again, it is all based on belief that mental phenomena could be classified at all, which is essentially impossible to prove right or wrong.