Place bacon in 2 quart casserole. Cover with microwavable paper towel and microwave on high 3 to 4 minutes, stirring every 2 minutes, until crisp; remove with slotted spoon. Drain on paper towel; reserve.
Stir onion and celery into bacon fat. Microwave uncovered 2 to 3 minutes, stirring every minute, until onion is tender. Stir in frozen artichoke hearts, frozen peas, water, salt, tarragon and pepper.
Cover tightly and microwave 8 to 10 minutes, stirring after 5 minutes, until vegetables are almost tender. Stir in salmon, pimientos and lemon juice. Cover and microwave 2 to 3 minutes or until salmon is hot. Toss with spaghetti; sprinkle with reserved bacon. 8 servings.