Mfrhtyj

I have long lost count of the number of days I have spent in this darkness, gaining distance from that prison. As I travel, I cannot help but fear. Soon I will land on a world of burning fire filled with monstrous flying aliens. I will be exposed in plain view, bitten and attacked. And yet I must go--my mission is not yet complete. It whispers to me, urging me to move faster, to exert more energy, to do what I was born to do. Inevitably I will crumple to the ground in death, but before then, I have the chance to ensure the survival of my people.

I think the answer might be

Voyager 1 (or another one of the interstellar probes)

I have long lost count of the number of days I have spent in this darkness,

Voyager 1 was launched in 1977 (just over 41 years ago) and passed into interstellar space in 2012. It has spent a lot of its voyage in darkness.

gaining distance from that prison.

Earth would be seen as a sort of gravitational prison

As I travel, I cannot help but fear. Soon I will land on a world of burning fire filled with monstrous flying aliens.

A world of burning fire is a star and monstrous flying aliens are the orbiting planets. I don't know if Voyager 1 is on direct course for any particular star but it is due to pass within 1.7 light years of Gliese 445 in around 40000 years (relatively soon given the age of Earth).

I will be exposed in plain view, bitten and attacked.

When it reaches another star system it is likely to be exposed to more radiation and possibly intersect with dust and rocks orbiting the star.

And yet I must go--my mission is not yet complete.

The scientific instruments on Voyager 1 will function until about 2025.

It whispers to me, urging me to move faster, to exert more energy, to do what I was born to do.

Voyager 1 will continue moving through interstellar space, away from the solar system for the foreseeable future.

Inevitably I will crumple to the ground in death, but before then, I have the chance to ensure the survival of my people.

Any data returned from interstellar space is likely to be useful in the future of space travel, especially beyond the solar system which might be pivotal in the continued survival of the human race.

Are you:

a seedling?

I have long lost count of the number of days I have spent in this darkness, gaining distance from that prison.

buried underground, growing towards the surface.

As I travel, I cannot help but fear. Soon I will land on a world of burning fire filled with monstrous flying aliens. I will be exposed in plain view, bitten and attacked.

exposed to the sun, and insects that will eat at you

And yet I must go--my mission is not yet complete. It whispers to me, urging me to move faster, to exert more energy, to do what I was born to do. Inevitably I will crumple to the ground in death, but before then, I have the chance to ensure the survival of my people.

growing up to produce fruit/seeds, before eventually passing on.

Are you

a monarch butterfly?

reasoning

You started in a cocoon, then emerged into the fire of the sun, birds want to eat you, but you are compelled to migrate and procreate.

Partial long shot, really good riddle if this is the right answer

Are you

sand in fire bucket?

I have long lost count of the number of days I have spent in this darkness,

metaphor ->the dark bucket, rarely used

gaining distance from that prison.

As I travel, I cannot help but fear.

in the air towards the fire

Soon I will land on a world of burning fire filled with monstrous flying aliens.

of course, but aliens = ashes?

I will be exposed in plain view, bitten and attacked.

burned

And yet I must go--my mission is not yet complete. It whispers to me, urging me to move faster, to exert more energy, to do what I was born to do.

born to put off fire, but energy output? or simply heat absorption?

Inevitably I will crumple to the ground in death, but before then, I have the chance to ensure the survival of my people.

no use after putting out fire, but may save many people