Was the Viswamitra of Gayatri Mantra in Rig Veda the same that appears in Ramayana?

Mandala 3 of Rig Veda comprises 62 hymns, mainly to Agni and Indra and the Vishvedevas. The verse 3.62.10 has great importance in Hinduism as the Gayatri Mantra. Most hymns in this book are attributed to viśvāmitra gāthinaḥ.

Rigveda 

It was said that this Mantra had been known as "Savitri Mantra" and composed in Gayatri Meter, dedicated to Savitr, the sun deity.

In Ramayana it was referred to parama matra - परमम्

तस्य ऋषेः परम उदारम् वचः श्रुत्वा नृप नरोत्तमौ |
स्नात्वा कृत उदकौ वीरौ जेपतुः परमम् जपम् || १-२३-३

On hearing the benign words of the sage those valorous and best ones among men got up, bathed, and on offering water oblation they mediated upon the supreme hymn

Later people started calling it as Gayatri Mantra.

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So the family of Sage Viswamitra, according to Rig Veda, composed it. It can be anyone of his family including Sage Viswamitra. Further, it was not mentioned that he was a King before becoming a Sage. 

The Story of King Viswamitra becoming a sage appears in Ramayana only.