So, of course there is no such thing as an "epistemology of emotion." One piece of settled understanding - justified belief - is that emotion is the hallmark of subjectivity and therefore the root of opinion. Feelings are directly felt by the mind, and the mind is that which is most subjective about us.
But I'd say that any theory of mind is fluid, and that it's conjectural at best that mind can exist in a subjective state. I suppose that we know what we know because it can be affirmed by others. Scientific knowledge is of the sort that must be agreed to by any non-perverse interlocutor. That's what science means. I suppose that "epistemology of science" is redundant.
Objective proof means shared and repeatable procedural validation. Objective proof is justified belief, but it started as belief. Belief motivates a seeking for truth, which justifies the belief.
I am obviously no academic, nor even an amateur philosopher. I would only like to state the obvious. In this case, I'd say it's obvious that one way to define emotion is that it is the felt knowledge of a match between subjective and objective understanding. Which is to say that conscious mind - all the way "down" to ants - is about matching the generalized abstractions made from prior observation with the current conjectural observations about what is going on in front of you. The match is felt emotionally. Emotion is the match.
Emotion is how we survive as living creatures. We justify our beliefs when they enable us to survive. Emotion is quicker than cognition. We re-cognize a lion or a friend based on prior experience. The more cognitive experience you have, the more quickly you might re-cognize. Cloned ants crossing (their own) paths feel which way to go. An ant hive is a mind of sorts. Is there an inside to it?
Nearly all of us fall prey to the fiction that there is something "in" the mind. We think of memories and narratives and words and sometimes we think that our mind "holds" a replica of the world all about us. It's funny that we don't think that about computers. They only hold numbers composed of zeros and ones and they programmatically deploy them according to some set of ordered operations to create simulacra and words that humans might re-cognize. They cannot be minds.
I agree with Ricardo Manzotti that what we call our mind is composed of perceptions and delayed perceptions (perhaps endlessly looping present perceptions) and that there is nothing inside the mind which is a replica of those perceptions, which always exist in a spread condition without the mind.
In just the way that I remember many specifics about JFK's assassination, some perceptions are singular and some are combined to form idealizations or generalizations about some collection of perceptions. The particulars are largely fogettable, once the ideal is formed. But our mind is never separable from the "objective" (shared) reality in which it is embedded. Of which it is a part.
Emotion energizes life. It predicts what will happen if and when we do or don't act. There is no will without emotion, including the will to know. Knowledge of any sort can't exist without emotion, and of course I would go so far as to say that there is no reality without emotion. Meaning that there is no life. There is no knower.
But there is always a knower, since not everything moves by force. Actual objective things move toward or away without the exchange of force-mediating particles on the basis of inertia, which also composes cosmic mind. The difference between force-mediated motion and non-force mediated emotion is (also) relative.
Emotion is simultaneous. What is felt is a desire to move. God is love. Godless reality is entropic and disappears quickly. A particle at light speed is inertial, or stationary, to the particle having mass. Emotion is always precognition.
So there you have it; an epistemology of emotion. Who knew??