Sat-svarūpah, of the nature of Existence
Sat-Existence which is remains in 3 periods of time (past, present, future).
If śruti said that I am that Brahman which is never ceases to be, how about when one die? In the analysis of 3 bodies, we learned that our body, which is the product of tamas aspect of grossification process of 5 mahabhutas, is not me. It is not my true nature, therefore even is negated, I am still there. But we also need to see the fact that the effect is the not different from the cause, whereas the cause is not the effect. In the world of clay, the pot is clay only, but clay is not the pot. In the death body, the existence of Cit-consciousness is continue to be there, but the medium (death body) doesn't reflect Cit-consciousness, therefore it is inert. Just like the sunlight is reflected in a bucket of water, but when you emptied the bucket, it can not reflect the sunlight anymore, even though sunlight continue to be there.
Similarly in any object, consciousness is not limited by time, it is always remains in past, present and future. To be called as past or future, anything need to be as present. So these 3 periods of time can be reduced into 1 present only. And to know the present exist, consciousness must be there. Therefore time is superimposed (having the basis) upon consciousness. So we can see that Cit is invariable present in 3 periods of times which is called Sat-Existence.
Ānanda-svarūpah, of the nature of Happiness / Bliss
I Ātma who is equated to limitless Brahman manifest through the mind is experiential happiness. One is said to be happy, when one's will is fulfilled. The wanting person is being suspended, therefore the fullness / limitless (anantam) nature is being manifested.
There is a lot of definition of Brahman like ajam-unborn, avyayam-indeclinable, acintyam-incomprehensible, etc, but why sat-cit-ānanda is giving the importance when the equation of me and Brahman is made? Because there is 3 fold of conclusion made by Jīva and they make the Jīva struggle:
1. I am mortal, therefore the fear of death is there, where one doesn't know his/her true nature is ever exist.
2. I am unhappy, therefore one keep struggling look for happiness and look for someone who can give him/her happiness, where one doesn't know his/her true nature is fullness / limitless.
3. I am ignorance, therefore one keep wanting to know and need other's acknowledgement, when one doesn't know his/her true nature is consciousness / knowledge.